Methods of detecting a quantity of water in a humidifier

ABSTRACT

Methods of an apparatus determine a quantity of a body of water in a humidifier such as by indirect measurement. The quantity of water may be determined by measuring one or more properties or characteristics, from which the quantity of water may be inferred. Characteristics of a flow of air, the humidifier, and/or the body of water may be measured. The characteristics may be, for example, pressure, flow rate, noise, vibration, temperature, electrical or mechanical. These may be measured by one or more sensors, which may be located in the humidifier, RPT device, air circuit or the patient interface. The methods described may have advantages, for example in being able to detect the quantity of water without requiring sensors to be present in a disposable component, and in some cases, without introduction of additional sensors.

1 CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/030,402 filed Apr. 19, 2016 which is a national phase entry under 35U.S.C. § 371 of International Application No. PCT/AU2014/050286 filedOct. 14, 2014, published in English, which claims priority from NewZealand Patent Application No. 629531 filed Aug. 29, 2014 and AustralianProvisional Patent Application No. 2013904049 filed Oct. 21, 2013, allof which are incorporated herein by reference.

2 BACKGROUND OF THE TECHNOLOGY 2.1 Field of the Technology

The present technology relates to one or more of the detection,diagnosis, treatment, prevention and amelioration of respiratory-relateddisorders. The present technology also relates to medical devices orapparatus, and their use.

2.2 Description of the Related Art 2.2.1 Human Respiratory System andits Disorders

The respiratory system of the body facilitates gas exchange. The noseand mouth form the entrance to the airways of a patient.

The airways include a series of branching tubes, which become narrower,shorter and more numerous as they penetrate deeper into the lung. Theprime function of the lung is gas exchange, allowing oxygen to move fromthe air into the venous blood and carbon dioxide to move out. Thetrachea divides into right and left main bronchi, which further divideeventually into terminal bronchioles. The bronchi make up the conductingairways, and do not take part in gas exchange. Further divisions of theairways lead to the respiratory bronchioles, and eventually to thealveoli. The alveolated region of the lung is where the gas exchangetakes place, and is referred to as the respiratory zone. See“Respiratory Physiology”, by John B. West, Lippincott Williams &Wilkins, 9th edition published 2011.

A range of respiratory disorders exist. Certain disorders may becharacterised by particular events, e.g., apneas, hypopneas, andhyperpneas.

Obstructive Sleep Apnea (OSA), a form of Sleep Disordered Breathing(SDB), is characterized by events including occlusion or obstruction ofthe upper air passage during sleep. It results from a combination of anabnormally small upper airway and the normal loss of muscle tone in theregion of the tongue, soft palate and posterior oropharyngeal wallduring sleep. The condition causes the affected patient to stopbreathing for periods typically of 30 to 120 seconds in duration,sometimes 200 to 300 times per night. It often causes excessive daytimesomnolence, and it may cause cardiovascular disease and brain damage.The syndrome is a common disorder, particularly in middle agedoverweight males, although a person affected may have no awareness ofthe problem. See U.S. Pat. No. 4,944,310 (Sullivan).

Cheyne-Stokes Respiration (CSR) is another form of sleep disorderedbreathing. CSR is a disorder of a patient's respiratory controller inwhich there are rhythmic alternating periods of waxing and waningventilation known as CSR cycles. CSR is characterised by repetitivede-oxygenation and re-oxygenation of the arterial blood. It is possiblethat CSR is harmful because of the repetitive hypoxia. In some patients,CSR is associated with repetitive arousal from sleep, which causessevere sleep disruption, increased sympathetic activity, and increasedafterload. See U.S. Pat. No. 6,532,959 (Berthon-Jones).

Obesity Hyperventilation Syndrome (OHS) is defined as the combination ofsevere obesity and awake chronic hypercapnia, in the absence of otherknown causes for hypoventilation. Symptoms include dyspnea, morningheadache and excessive daytime sleepiness.

Chronic Obstructive Pulmonary Disease (COPD) encompasses any of a groupof lower airway diseases that have certain characteristics in common.These include increased resistance to air movement, extended expiratoryphase of respiration, and loss of the normal elasticity of the lung.Examples of COPD are emphysema and chronic bronchitis. COPD is caused bychronic tobacco smoking (primary risk factor), occupational exposures,air pollution and genetic factors. Symptoms include: dyspnea onexertion, chronic cough and sputum production.

Neuromuscular Disease (NMD) is a broad term that encompasses manydiseases and ailments that impair the functioning of the muscles eitherdirectly via intrinsic muscle pathology, or indirectly via nervepathology. Some NMD patients are characterised by progressive muscularimpairment leading to loss of ambulation, being wheelchair-bound,swallowing difficulties, respiratory muscle weakness and, eventually,death from respiratory failure. Neuromuscular disorders can be dividedinto rapidly progressive and slowly progressive: (i) Rapidly progressivedisorders: Characterised by muscle impairment that worsens over monthsand results in death within a few years (e.g., Amyotrophic lateralsclerosis (ALS) and Duchenne muscular dystrophy (DMD) in teenagers);(ii) Variable or slowly progressive disorders: Characterised by muscleimpairment that worsens over years and only mildly reduces lifeexpectancy (e.g., Limb girdle, Facioscapulohumeral and Myotonic musculardystrophy). Symptoms of respiratory failure in NMD include: increasinggeneralised weakness, dysphagia, dyspnea on exertion and at rest,fatigue, sleepiness, morning headache, and difficulties withconcentration and mood changes.

Chest wall disorders are a group of thoracic deformities that result ininefficient coupling between the respiratory muscles and the thoraciccage. The disorders are usually characterised by a restrictive defectand share the potential of long term hypercapnic respiratory failure.Scoliosis and/or kyphoscoliosis may cause severe respiratory failure.Symptoms of respiratory failure include: dyspnea on exertion, peripheraloedema, orthopnea, repeated chest infections, morning headaches,fatigue, poor sleep quality and loss of appetite.

A range of therapies have been used to treat or ameliorate suchconditions. Furthermore, otherwise healthy individuals may takeadvantage of such therapies to prevent respiratory disorders fromarising. However, these have a number of shortcomings.

2.2.2 Therapy

Continuous Positive Airway Pressure (CPAP) therapy has been used totreat Obstructive Sleep Apnea (OSA). The hypothesis is that continuouspositive airway pressure acts as a pneumatic splint and may preventupper airway occlusion by pushing the soft palate and tongue forward andaway from the posterior oropharyngeal wall. Treatment of OSA by CPAPtherapy may be voluntary, and hence patients may elect not to complywith therapy if they find devices used to provide such therapy one ormore of: uncomfortable, difficult to use, expensive and aestheticallyunappealing.

Non-invasive ventilation (NIV) provides ventilatory support to a patientthrough the upper airways to assist the patient in taking a full breathand/or maintain adequate oxygen levels in the body by doing some or allof the work of breathing. The ventilatory support is provided via apatient interface. NIV has been used to treat CSR, OHS, COPD, MD andChest Wall disorders. In some forms, the comfort and effectiveness ofthese therapies may be improved.

Invasive ventilation (IV) provides ventilatory support to patients thatare no longer able to effectively breathe themselves and may be providedusing a tracheostomy tube. In some forms, the comfort and effectivenessof these therapies may be improved.

2.2.3 Diagnosis and Treatment Systems

These therapies may be provided by a treatment system or device. Systemsand devices may also be used to diagnose a condition without treatingit.

A treatment system may comprise a Respiratory Pressure Therapy Device(RPT device), an air circuit, a humidifier, a patient interface, anddata management.

2.2.3.1 Patient Interface

A patient interface may be used to interface respiratory equipment toits wearer, for example by providing a flow of air to an entrance to theairways. The flow of air may be provided via a mask to the nose and/ormouth, a tube to the mouth or a tracheostomy tube to the trachea of apatient. Depending upon the therapy to be applied, the patient interfacemay form a seal, e.g., with a region of the patient's face, tofacilitate the delivery of gas at a pressure at sufficient variance withambient pressure to effect therapy, e.g., at a positive pressure ofabout 10 cmH₂O relative to ambient pressure. For other forms of therapy,such as the delivery of oxygen, the patient interface may not include aseal sufficient to facilitate delivery to the airways of a supply of gasat a positive pressure of about 10 cmH₂O.

The design of a patient interface presents a number of challenges. Theface has a complex three-dimensional shape. The size and shape of nosesvaries considerably between individuals. Since the head includes bone,cartilage and soft tissue, different regions of the face responddifferently to mechanical forces. The jaw or mandible may move relativeto other bones of the skull. The whole head may move during the courseof a period of respiratory therapy.

As a consequence of these challenges, some masks suffer from being oneor more of obtrusive, aesthetically undesirable, costly, poorly fitting,difficult to use, and uncomfortable, especially when worn for longperiods of time or when a patient is unfamiliar with a system. Forexample, masks designed solely for aviators, masks designed as part ofpersonal protection equipment (e.g., filter masks), SCUBA masks, or forthe administration of anaesthetics may be tolerable for their originalapplication, but nevertheless such masks may be undesirablyuncomfortable to be worn for extended periods of time, e.g., severalhours. This discomfort may lead to a reduction in patient compliancewith therapy. This is even more so if the mask is to be worn duringsleep.

CPAP therapy is highly effective to treat certain respiratory disorders,provided patients comply with therapy. If a mask is uncomfortable, ordifficult to use a patient may not comply with therapy. Since it isoften recommended that a patient regularly wash their mask, if a mask isdifficult to clean (e.g., difficult to assemble or disassemble),patients may not clean their mask and this may impact on patientcompliance.

While a mask for other applications (e.g., aviators) may not be suitablefor use in treating sleep disordered breathing, a mask designed for usein treating sleep disordered breathing may be suitable for otherapplications.

For these reasons, patient interfaces for delivery of CPAP during sleepform a distinct field.

2.2.3.2 Respiratory Pressure Therapy (RPT) Device

Air pressure generators are known in a range of applications, e.g.,industrial-scale ventilation systems. However, air pressure generatorsfor medical applications have particular requirements not fulfilled bymore generalised air pressure generators, such as the reliability, sizeand weight requirements of medical devices. In addition, even devicesdesigned for medical treatment may suffer from shortcomings, pertainingto one or more of: comfort, noise, ease of use, efficacy, size, weight,manufacturability, cost, and reliability.

An example of the special requirements of certain RPT devices isacoustic noise.

Table of noise output levels of prior RPT devices (one specimen only,measured using test method specified in ISO3744 in CPAP mode at 10cmH₂O).

A-weighted sound power Year RPT Device name level dB(A) (approx.)C-Series Tango ™ 31.9 2007 C-Series Tango ™ with Humidifier 33.1 2007 S8Escape ™ II 30.5 2005 S8 Escape ™ II with H4i ™ Humidifier 31.1 2005 S9AutoSet ™ 26.5 2010 S9 AutoSet ™ with H5i ™ Humidifier 28.6 2010

One known RPT device used for treating sleep-disordered breathing is theS9 Sleep Therapy System, manufactured by ResMed Limited. Another exampleof an RPT device is a ventilator. Ventilators such as the ResMedStellar™ Series of Adult and Paediatric Ventilators may provide supportfor invasive and non-invasive non-dependent ventilation for a range ofpatients for treating a number of conditions such as but not limited toNMD, OHS and COPD.

The ResMed Elisée™ 150 ventilator and ResMed VS III™ ventilator mayprovide support for invasive and non-invasive dependent ventilationsuitable for adult or paediatric patients for treating a number ofconditions. These ventilators provide volumetric and barometricventilation modes with a single or double limb circuit. RPT devicestypically comprise a pressure generator, such as a motor-driven bloweror a compressed gas reservoir, and are configured to supply a flow ofair to the airway of a patient. In some cases, the flow of air may besupplied to the airway of the patient at positive pressure. The outletof the RPT device is connected via an air circuit to a patient interfacesuch as those described above.

2.2.4 Humidifier

Delivery of a flow of air without humidification may cause drying ofairways. The use of a humidifier with a RPT device and the patientinterface produces humidified gas that minimizes drying of the nasalmucosa and increases patient airway comfort. In addition, in coolerclimates, warm air applied generally to the face area in and about thepatient interface is more comfortable than cold air. A range ofartificial humidification devices and systems are known, however theymay not fulfil the specialised requirements of a medical humidifier.

Medical humidifiers are used to increase humidity and/or temperature ofthe flow of air in relation to ambient air when required, typicallywhere the patient may be asleep or resting (e.g., at a hospital). Amedical humidifier for bedside placement may be small. A medicalhumidifier may be configured to only humidify and/or heat the flow ofair delivered to the patient without humidifying and/or heating thepatient's surroundings. Room-based systems (e.g., a sauna, an airconditioner, or an evaporative cooler), for example, may also humidifyair that is breathed in by the patient; however, those systems wouldalso humidify and/or heat the entire room, which may cause discomfort tothe occupants. Furthermore, medical humidifiers may have more stringentsafety constraints than industrial humidifiers.

While a number of medical humidifiers are known, they can suffer fromone or more shortcomings. Some medical humidifiers may provideinadequate humidification, and some are difficult or inconvenient to useby patients.

Humidity refers to the quantity of water vapour present in the air. Itis commonly measured in two ways:

(1) Absolute Humidity (AH) is the actual content of water vapour in theair recorded in terms of weight per volume—usually in grams per cubicmeter (g/m3) or milligrams per liter (mg/L).(2) Relative Humidity (RH) is a percentage expression of the actualwater vapour content of a gas compared to its capacity to carry watervapour at any given temperature.

The capacity of air to hold water vapour increases as the temperature ofthe air increases. This means that for air with a stable AH, the RH willdecline as the temperature of the air is increased. Conversely, for airsaturated with water (100% RH), if the temperature is reduced then theexcess water will condense out. Air breathed by humans is generallynaturally heated and humidified by the patient's airways to reach atemperature of 37° C. and 100% humidity. At this temperature, theabsolute humidity (AH) is 44 mg/L.

Medical humidifiers are available in many forms. A medical humidifiermay be a standalone device that is coupled to an RPT device via an aircircuit, integrated with the RPT device or configured to be directlycoupled to the relevant RPT device. While passive humidifiers canprovide some relief, generally, a heated humidifier is required toprovide sufficient humidity and temperature to the air so that thepatient will be comfortable. Humidifiers typically comprise a humidifierreservoir (also referred to as water reservoir or tub) having a capacityof several hundred milliliters (ml), a heating element for heating thewater in the reservoir, a control to enable the level of humidificationto be varied, a gas inlet to receive gas from the flow generator ordevice, and a gas outlet adapted to be connected to an air circuit thatdelivers the humidified gas to the patient interface.

A heated passover humidifier is one common form of humidifier used witha RPT device. In such humidifiers, the heating element may beincorporated in a heating plate which sits under, and is in thermalcontact with, the humidifier reservoir. Thus, heat is transferred fromthe heating plate to the humidifier reservoir primarily by conduction.The air flow from the RPT device or flow generator or ventilator passesover the heated water in the water tub, resulting in water vapour beingtaken up by the air flow. The ResMed H4i™ and H5i™ Humidifiers areexamples of such heated passover humidifiers that are used incombination with ResMed S8 and S9 CPAP systems respectively.

Other humidifiers may also be used, such as a bubble or diffuserhumidifier, a jet humidifier or a wicking humidifier.

An alternative form of humidification is provided by the ResMedHumiCare™ D900 humidifier that uses a CounterStream™ technology thatdirects the air flow over a large surface area in a first direction,whilst supplying heated water to the large surface area in a secondopposite direction. The ResMed HumiCare™ D900 humidifier may be usedwith a range of invasive and non-invasive ventilators.

3 BRIEF SUMMARY OF THE TECHNOLOGY

The present technology is directed towards providing medical devicesused in the diagnosis, amelioration, treatment, or prevention ofrespiratory disorders having one or more of improved comfort, cost,efficacy, ease of use and manufacturability.

A first aspect of the present technology relates to apparatus used inthe diagnosis, amelioration, treatment or prevention of a respiratorydisorder.

Another aspect of the present technology relates to methods used in thediagnosis, amelioration, treatment or prevention of a respiratorydisorder.

An aspect of certain forms of the present technology is to providemethods and/or apparatus that improve the compliance of patients withrespiratory therapy.

One form of the present technology relates to a method of determining aquantity of a body of liquid in a humidifier.

Some versions of the present technology may involve a method ofdetermining a reservoir water quantity of a humidifier. The method mayinclude providing a humidifier reservoir configured to contain water,the reservoir being in fluid communication with an inlet of thehumidifier. The method may further include delivering a flow of air tothe humidifier reservoir through the inlet of the humidifier. The methodmay further include determining a first measurement set from the flow ofair. The method may further include determining a reservoir waterquantity of the humidifier reservoir based on the first measurement set.

In some versions, the first measurement set may comprise one or moresensed values of any one or more of: a pressure, a temperature, a flowrate and a noise. In some versions, a sensed value of the firstmeasurement set may be determined with a first sensor at a locationdownstream of an outlet of the humidifier reservoir. In some versions,the location of the first sensor may be external to the humidifierreservoir. In some versions, a sensed value of the first measurement setmay be determined with a first sensor located outside of the humidifierreservoir. In some versions, the reservoir water quantity may bedetermined with the first measurement set and reference data. In someversions, the reference data may comprise a second measurement setincluding one or more sensed values.

In some versions, the second measurement set may comprise one or moresensed values of one or more of: a pressure, a temperature, a flow rateand a noise. In some versions, the second measure set may be determinedsubsequent to determination of the first measure set. In some versions,the second measure set may be determined at least a predetermined lengthof time subsequent to determination of the first measure set. In someversions, the reference data may comprise one or more estimates of oneor more of: a pressure, a temperature, a flow rate and a noise. In someversions, the one or more estimates may be based on one or more of: amotor current, a motor speed, a motor acceleration, an altitude, atherapy pressure and a flow rate. In some versions, determining thereservoir water quantity may be based on a function of the referencedata and the first measurement set.

In some versions, the function may determine a change in magnitude ofone or more values of the reference data and the first measurement set.In some versions, the function may determine a change in phase of one ormore values of the reference data and the first measurement set. In someversions, the function may determine a time lag with one or more valuesof the reference data and the first measurement set. In some versions,the reference data may comprise one or more sensed values determinedwith a second sensor at a location different from the first sensor. Insome versions, the second sensor may be located upstream of thehumidifier reservoir. In some versions, the reservoir water quantity maybe determined by locating a value in a look-up table with a value of thefirst measurement set.

In some versions, the method may include performing a calibration cycleto populate one or more values in the look-up table. In some versions,the reservoir water quantity may be determined with a function. In someversions, the method may include performing a calibration cycle todetermine the function. In some versions, the calibration cycle may beperformed while the humidifier reservoir is in use. In some versions,the calibration cycle may be performed during a set-up process. In someversions, the calibration cycle may be repeated at predetermined timeintervals.

Some versions of the present technology may involve a control method ofa processor for indirectly determining a reservoir water quantity of ahumidifier having a reservoir to contain water, the humidifier having aninlet and an outlet. The method may include, in the processor,determining with a first sensor a first property, the first propertycomprising one of a characteristic of the humidifier, a characteristicof a flow of air through the humidifier, and a characteristic of thewater in the humidifier reservoir. The method may further include, inthe processor, determining the reservoir water quantity based on thefirst property.

In some versions, the first property may comprise a capacitance orresistance of the water. In some versions, first property may comprise afrequency of a vibration in the humidifier reservoir. In some versions,the first property may comprise a pressure drop through the inlet of thehumidifier and the outlet of the humidifier. In some versions, the firstproperty may comprise a time lag through the inlet and the outlet of thehumidifier. In some versions, the first property may comprise a torqueof a rotatable paddle in the humidifier. In some versions, the firstproperty may comprise a noise in the humidifier.

In some versions, the first property may comprise density of air throughthe humidifier. In some versions, the method may include determining achange with respect to first and second measurements of the firstproperty, wherein the reservoir water quantity is determined from thedetermined change. In some versions, the method may include accessing atable of reservoir water quantity values in correlation with a valueattributable to the first property. In some versions, the method mayinclude controlling an adjustment of an operation of a respiratorytreatment apparatus based on the determined reservoir water quantity. Insome versions, the adjustment may comprise a change to a rate ofhumidification.

Some versions of the present technology may involve an apparatus forhumidifying a flow of air to be delivered to a patient. The apparatusmay include an inlet to receive the flow of air. The apparatus mayfurther include a humidifier reservoir configured to contain a body ofwater for humidifying the flow of air, the humidifier reservoir being influid communication with the inlet. The apparatus may further include afirst sensor configured to determine a first measurement set from theflow of air. The apparatus may further include a controller, wherein thecontroller is configured to determine a reservoir water quantity of thehumidifier reservoir based on the first measurement set.

In some versions, the first measurement may comprise one or more sensedvalues of one or more of: a pressure, a temperature, a flow rate and anoise. In some versions, the first sensor may be located to sense valuesdownstream of the humidifier reservoir. In some versions, the firstsensor may be located external to the humidifier reservoir. In someversions, the controller may be configured to determine a quantity ofthe body of water based on the first measurement set and reference data.In some versions, the reference data may comprise a second measurementset including one or more sensed values. In some versions, the secondmeasurement set may comprise one or more sensed values of one or moreof: a pressure, a temperature, a flow rate and a noise. In someversions, the reference data may comprise one or more estimates of oneor more of: a pressure, a temperature, a flow rate and a noise.

In some versions, the one or more estimates may be based on one or moreof: a motor current, a motor speed, a motor acceleration, an altitude, atherapy pressure and a flow rate. In some versions, the controller maybe further configured to determine the quantity of the body of waterbased on a relationship between the reference data and the firstmeasurement set. In some versions, the relationship may include one ormore of a change in magnitude, a change in phase, or a time lag betweenone or more values of the reference data and the first measurement set.In some versions, the controller may be further configured to determinethe reservoir water quantity by finding one or more values in a look-uptable corresponding to the first measurement or by processing a functionon one or more values of the first measurement set. In some versions,the controller may be further configured to perform a calibration cycleto populate the one or more values in the look-up table or to derive thefunction.

Some versions of the present technology may involve an apparatus forhumidifying a flow of air to be delivered to a patient, the apparatusfor indirectly determining a reservoir water quantity. The apparatus mayinclude a humidifier reservoir configured to contain a body of water forhumidifying a flow of air, the humidifier reservoir being in fluidcommunication with an inlet and an outlet for the flow of air. Theapparatus may further include one or more sensors. The apparatus mayfurther include a controller coupled with the one or more sensors, thecontroller being configured to determine with the one or more sensors afirst property, the first property comprising one of a characteristic ofthe humidifier, a characteristic of a flow of air through thehumidifier, and a characteristic of water in the humidifier reservoir,the controller being further configured to determine the reservoir waterquantity based on the first property.

In some versions, the first property may comprise a capacitance orresistance of the water. In some versions, the first property maycomprise a frequency of a vibration in the humidifier reservoir. In someversions, the first property may comprise a pressure drop through aninlet of the humidifier and the outlet of the humidifier. In someversions, the first property may comprise a time lag through the inletand the outlet of the humidifier. In some versions, the first propertymay comprise a torque of a rotatable paddle in the humidifier. In someversions, the first property may comprise a noise in the humidifier. Insome versions, the first property may comprise density of air throughthe humidifier.

In some versions, the controller may be further configured to determinea change with respect to first and second measurements of the firstproperty, wherein the reservoir water quantity is determined from thedetermined change. In some versions, the controller may be furtherconfigured to access a table of reservoir water quantity values incorrelation with a value attributable to the first property. In someversions, the controller may be further configured to make an adjustmentof an operation of a respiratory treatment apparatus based on thedetermined reservoir water quantity. In some versions, the adjustmentmay comprise a change to a rate of humidification.

Of course, portions of the aspects may form sub-aspects of the presenttechnology. Also, various ones of the sub-aspects and/or aspects may becombined in various manners and may also constitute additional aspectsor sub-aspects of the present technology.

Other features of the technology will be apparent from consideration ofthe information contained in the following detailed description,abstract, drawings and claims.

4 BRIEF DESCRIPTION OF THE DRAWINGS

The present technology is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawings, in whichlike reference numerals refer to similar elements including:

4.1 Treatment Systems

FIG. 1A shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a nasal pillows, receiving a supply ofair at positive pressure from an RPT device 4000. Air from the RPTdevice is humidified in a humidifier 5000, and passes along an aircircuit 4170 to the patient 1000. A bed partner 1100 is also shown.

FIG. 1B shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a nasal mask, receiving a supply of airat positive pressure from an RPT device 4000. Air from the RPT device ishumidified in a humidifier 5000, and passes along an air circuit 4170 tothe patient 1000.

FIG. 1C shows a system including a patient 1000 wearing a patientinterface 3000, in the form of a full-face mask, receiving a supply ofair at positive pressure from an RPT device 4000. Air from the RPTdevice is humidified in a humidifier 5000, and passes along an aircircuit 4170 to the patient 1000.

4.2 Respiratory System and Facial Anatomy

FIG. 2A shows an overview of a human respiratory system including thenasal and oral cavities, the larynx, vocal folds, esophagus, trachea,bronchus, lung, alveolar sacs, heart and diaphragm.

FIG. 2B shows a view of a human upper airway including the nasal cavity,nasal bone, lateral nasal cartilage, greater alar cartilage, nostril,lip superior, lip inferior, larynx, hard palate, soft palate,oropharynx, tongue, epiglottis, vocal folds, esophagus and trachea.

FIG. 2C is a front view of a face with several features of surfaceanatomy identified including the lip superior, upper vermilion, lowervermilion, lip inferior, mouth width, endocanthion, a nasal ala,nasolabial sulcus and cheilion. Also indicated are the directionssuperior, inferior, radially inward and radially outward.

4.3 Patient Interface

FIG. 3A shows a patient interface in the form of a nasal mask inaccordance with one form of the present technology.

4.4 RPT Device

FIG. 4A shows an RPT device in accordance with one form of the presenttechnology.

FIG. 4B is a schematic diagram of the pneumatic path of a RPT device inaccordance with one form of the present technology. The directions ofupstream and downstream are indicated.

FIG. 4C is a schematic diagram of the electrical components of a RPTdevice in accordance with one form of the present technology.

4.5 Humidifier

FIG. 5A shows an isometric view of a humidifier in accordance with oneform of the present technology.

FIG. 5B shows a schematic of a humidifier in accordance with one form ofthe present technology.

FIG. 5C shows an isometric view of a humidifier in accordance with oneform of the present technology.

FIG. 5D shows an isometric view of a humidifier in accordance with oneform of the present technology, showing a humidifier reservoir 5110removed from the humidifier reservoir dock 5130.

FIG. 6 shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the humidifier comprises a first sensor locatedupstream of the reservoir and a second sensor located downstream of thereservoir.

FIG. 6A shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the humidifier comprises a first pressure sensorlocated upstream of the reservoir and a second pressure sensor locateddownstream of the reservoir.

FIG. 6B shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the humidifier comprises a first microphone locatedupstream of the reservoir and a second microphone located downstream ofthe reservoir.

FIG. 6C shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the humidifier comprises a first sensor located inthe reservoir and a second sensor located downstream of the reservoir,proximal to a patient interface.

FIG. 7 shows an exemplary one-dimensional look-up table according to oneaspect of the present technology.

FIG. 8 shows an exemplary two-dimensional look-up table according to oneaspect of the present technology.

FIG. 9 shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the humidifier comprises a sensor located downstreamof the reservoir.

FIG. 9A shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the humidifier comprises a pressure sensor locateddownstream of the reservoir.

FIG. 9B shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the humidifier comprises a flow rate sensor locateddownstream of the reservoir.

FIG. 9C shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the humidifier comprises a microphone locateddownstream of the reservoir.

FIG. 10 shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the respiratory treatment system comprises avibration source and a vibration sensor.

FIG. 11A shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the respiratory treatment system comprises a movableportion and an optical sensor.

FIG. 11B shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the respiratory treatment system comprises a movableportion and an angular sensor.

FIG. 11C shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the respiratory treatment system comprises a movableportion and a proximity sensor.

FIG. 12A shows an exemplary schematic of a respiratory treatment systemcomprising a humidifier according to one aspect of the presenttechnology, wherein the humidifier comprises a rotatable paddle.

5 DETAILED DESCRIPTION OF EXAMPLES OF THE TECHNOLOGY

Before the present technology is described in further detail, it is tobe understood that the technology is not limited to the particularexamples described herein, which may vary. It is also to be understoodthat the terminology used in this disclosure is for the purpose ofdescribing only the particular examples discussed herein, and is notintended to be limiting.

The following description is provided in relation to various exampleswhich may share one or more common characteristics and/or features. Itis to be understood that one or more features of any one example may becombinable with one or more features of another example or otherexamples. In addition, any single feature or combination of features inany of the examples may constitute a further example.

5.1 Therapy

In one form, the present technology comprises a method for treating arespiratory disorder comprising the step of applying positive pressureto the entrance of the airways of a patient 1000.

In certain examples of the present technology, a supply of air atpositive pressure is provided to the nasal passages of the patient viaone or both nares.

In certain examples of the present technology, mouth breathing islimited, restricted or prevented.

5.2 Treatment Systems

In one form, the present technology comprises an apparatus or device fortreating a respiratory disorder. The apparatus or device may comprise aRPT device 4000 for supplying pressurised air to the patient 1000 via anair circuit 4170 to a patient interface 3000.

5.3 Patient Interface

A non-invasive patient interface 3000 in accordance with one aspect ofthe present technology comprises the following functional aspects (seeFIG. 3A): a seal-forming structure 3100, a plenum chamber 3200, apositioning and stabilising structure 3300 and one form of connectionport 3600 for connection to air circuit 4170. In one form, the patientinterface 3000 includes a forehead support 3700. In one form, thepatient interface 3000 includes a vent 3400 constructed and arranged toallow for the washout of exhaled carbon dioxide. In one form, thepatient interface 3000 includes at least one decoupling structure 3500,for example, a swivel or a ball and socket. In some forms, a functionalaspect may be provided by one or more physical components. In someforms, one physical component may provide one or more functionalaspects. In use, the seal-forming structure 3100 is arranged to surroundan entrance to the airways of the patient so as to facilitate the supplyof air at positive pressure to the airways.

5.4 RPT Device

An RPT device 4000 in accordance with one aspect of the presenttechnology (see FIGS. 4A and 4B) comprises mechanical and pneumaticcomponents 4100, electrical components 4200, and is configured toexecute one or more algorithms. The RPT device may have an externalhousing 4010, formed in two parts, an upper portion 4012 and a lowerportion 4014. Furthermore, the external housing 4010 may include one ormore panel(s) 4015. The RPT device 4000 comprises a chassis 4016 thatsupports one or more internal components of the RPT device 4000. The RPTdevice 4000 may include a handle 4018.

The pneumatic path of the RPT device 4000 may comprise one or more airpath items, e.g., an inlet air filter 4112, an inlet muffler 4122, apressure generator 4140 capable of supplying air at positive pressure(e.g., a blower 4142), an outlet muffler 4124 and one or more sensors4270, such as pressure sensors 4272 and flow rate sensors 4274.

One or more of the air path items may be located within a removableunitary structure which will be referred to as a pneumatic block 4020.The pneumatic block 4020 may be located within the external housing4010. In one form a pneumatic block 4020 is supported by, or formed aspart of the chassis 4016.

The RPT device 4000 may have an electrical power supply 4210, one ormore input devices 4220, a central controller 4230, a therapy devicecontroller 4240, a pressure generator 4140, one or more protectioncircuits 4250, memory 4260, sensors 4270, data communication interface4280 and one or more output devices 4290. Electrical components 4200 maybe mounted on a single Printed Circuit Board Assembly (PCBA) 4202. In analternative form, the RPT device 4000 may include more than one PCBA4202.

5.4.1 RPT Device Mechanical & Pneumatic Components

An RPT device may comprise one or more of the following components in anintegral unit. In an alternative form, one or more of the followingcomponents may be located as respective separate units.

5.4.1.1 Air Filter(s)

An RPT device in accordance with one form of the present technology mayinclude an air filter 4110, or a plurality of air filters 4110.

In one form, an inlet air filter 4112 is located at the beginning of thepneumatic path upstream of a pressure generator 4140. See FIG. 4B.

In one form, an outlet air filter 4114, for example an antibacterialfilter, is located between an outlet of the pneumatic block 4020 and apatient interface 3000. See FIG. 4B.

5.4.1.2 Muffler(s) 4120

In one form of the present technology, an inlet muffler 4122 is locatedin the pneumatic path upstream of a pressure generator 4140. See FIG.4B.

In one form of the present technology, an outlet muffler 4124 is locatedin the pneumatic path between the pressure generator 4140 and a patientinterface 3000. See FIG. 4B.

5.4.1.3 Pressure Generator 4140

In one form of the present technology, a pressure generator 4140 forproducing a flow, or a supply, of air at positive pressure is acontrollable blower 4142. For example the blower 4142 may include abrushless DC motor 4144 with one or more impellers housed in a volute.The blower may be capable of delivering a supply of air, for example ata rate of up to about 120 litres/minute, at a positive pressure in arange from about 4 cmH₂O to about 20 cmH₂O, or, in other examples, up toabout 30 cmH₂O. The blower may be as described in any one of thefollowing patents or patent applications, the contents of which areincorporated herein by reference in their entireties: U.S. Pat. Nos.7,866,944; 8,638,014; 8,636,479; and PCT Patent Application PublicationNo. WO 2013/020167.

The pressure generator 4140 may be under the control of the therapydevice controller 4240.

In other forms, a pressure generator 4140 may be a piston-driven pump, apressure regulator connected to a high pressure source (e.g., compressedair reservoir), or a bellows.

5.4.1.4 Sensor(s)

Sensors may be internal of the RPT device, or external of the RPTdevice. External sensors may be located for example on or form part ofthe air circuit, e.g., the patient interface. External sensors may be inthe form of non-contact sensors such as a Doppler radar movement sensorthat transmit or transfer data to the RPT device.

In one form of the present technology, one or more sensors 4270 arelocated upstream and/or downstream of the pressure generator 4140. Theone or more sensors 4270 may be constructed and arranged to measureproperties such as a flow rate, a pressure or a temperature at thatpoint in the pneumatic path.

In one form of the present technology, one or more sensors 4270 may belocated proximate to the patient interface 3000.

In one form, a signal from a sensor 4270 may be filtered, such as bylow-pass, high-pass or band-pass filtering.

5.4.1.4.1 Flow Rate Sensor

A flow rate sensor 4274 in accordance with the present technology may bebased on a differential pressure transducer, for example, an SDP600Series differential pressure transducer from SENSIRION.

In one form, a signal from the flow rate sensor 4274 is received by thecentral controller 4230.

Pressure Sensor 4272

A pressure sensor 4272 in accordance with the present technology islocated in fluid communication with the pneumatic path. An example of asuitable pressure transducer is a sensor from the HONEYWELL ASDX series.An alternative suitable pressure transducer is a sensor from the NPASeries from GENERAL ELECTRIC.

In one form, a signal from the pressure sensor 4272 is received by thecentral controller 4230.

5.4.1.4.1.1 Motor Speed Sensor

In one form of the present technology, a motor speed sensor 4276 is usedto determine a rotational velocity of the motor 4144 and/or the blower4142. A motor speed signal from the motor speed sensor 4276 may beprovided to the therapy device controller 4240. The motor speed sensor4276 may, for example, be a speed sensor, such as a Hall effect sensor.

5.4.1.5 Anti-Spill Back Valve

In one form of the present technology, an anti-spillback valve 4160 islocated between the humidifier 5000 and the pneumatic block 4020. Theanti-spillback valve 4160 is constructed and arranged to reduce the riskthat water will flow upstream from the humidifier 5000, for example, tothe motor 4144.

5.4.1.6 Air Circuit

An air circuit 4170 in accordance with an aspect of the presenttechnology is a conduit or a tube constructed and arranged in use toallow a flow of air to travel between two components such as thepneumatic block 4020 and the patient interface 3000.

In particular, the air circuit 4170 may be in fluid connection with theoutlet of the pneumatic block and the patient interface. The air circuitmay be referred to as an air delivery tube. In some cases, there may beseparate limbs of the circuit for inhalation and exhalation. In othercases, a single limb is used.

In some forms, the air circuit 4170 may comprise one or more heatingelements configured to heat air in the air circuit, for example, tomaintain or raise the temperature of the air. The heating element may bein a form of a heated wire circuit, and may comprise one or moresensors, such as temperature sensors. In one form, the heated wirecircuit may be helically wound around the axis of the air circuit 4170.The heating element may be in communication with a controller such as acentral controller 4230 or a humidifier controller 5250. One example ofan air circuit 4170 comprising a heated wire circuit is described inUnited States Patent Application No. US/2011/0023874, which isincorporated herewithin in its entirety by reference.

5.4.1.7 Supplemental Oxygen

In one form of the present technology, supplemental oxygen 4180 isdelivered to one or more points in the pneumatic path, such as upstreamof the pneumatic block 4020, to the air circuit 4170 and/or to thepatient interface 3000.

5.4.2 RPT Device Electrical Components (FIG. 4D) 5.4.2.1 Power Supply

A power supply 4210 may be located internal or external of the externalhousing 4010 of the RPT device 4000.

In one form of the present technology, power supply 4210 provideselectrical power to the RPT device 4000 only. In another form of thepresent technology, power supply 4210 provides electrical power to bothRPT device 4000 and humidifier 5000.

5.4.2.2 Input Devices

In one form of the present technology, a RPT device 4000 includes one ormore input devices 4220 in the form of buttons, switches or dials toallow a person to interact with the device. The buttons, switches ordials may be physical devices, or software devices accessible via atouch screen. The buttons, switches or dials may, in one form, bephysically connected to the external housing 4010, or may, in anotherform, be in wireless communication with a receiver that is in electricalconnection to the central controller 4230.

In one form, the input device 4220 may be constructed and arranged toallow a person to select a value and/or a menu option.

5.4.2.3 Central Controller

In one form of the present technology, the central controller 4230 isone or a plurality of processors suitable to control a RPT device 4000.

Suitable processors may include an x86 INTEL processor, a processorbased on ARM® Cortex®-M processor from ARM Holdings such as an STM32series microcontroller from ST MICROELECTRONIC. In certain alternativeforms of the present technology, a 32-bit RISC CPU, such as an STR9series microcontroller from ST MICROELECTRONICS or a 16-bit RISC CPUsuch as a processor from the MSP430 family of microcontrollers,manufactured by TEXAS INSTRUMENTS, may also be suitable.

In one form of the present technology, the central controller 4230 is adedicated electronic circuit.

In one form, the central controller 4230 is an application-specificintegrated circuit. In another form, the central controller 4230comprises discrete electronic components.

The central controller 4230 may be configured to receive input signal(s)from one or more sensors 4270, and one or more input devices 4220.

The central controller 4230 may be configured to provide outputsignal(s) to one or more of an output device 4290, a therapy devicecontroller 4240, a data communication interface 4280 and humidifiercontroller 5250.

In some forms of the present technology, the central controller 4230 isconfigured to implement the one or more methodologies described herein,such as the one or more algorithms expressed as computer programs storedin a non-transitory computer readable storage medium, such as memory4260. In some forms of the present technology, the central controller4230 may be integrated with a RPT device 4000. However, in some forms ofthe present technology, some methodologies may be performed by aremotely-located device. For example, the remotely-located device maydetermine control settings for a ventilator or may detect respiratoryrelated events by analysis of stored data such as from any of thesensors described herein.

5.4.2.4 Clock

The RPT device 4000 may include a clock 4232 that is connected to thecentral controller 4230.

5.4.2.5 Therapy Device Controller

In one form of the present technology, therapy device controller 4240 isa control module that forms part of the algorithms executed by thecentral controller 4230.

In one form of the present technology, therapy device controller 4240 isa dedicated motor control integrated circuit. For example, in one form,a MC33035 brushless DC motor controller, manufactured by ONSEMI is used.

5.4.2.6 Protection Circuits

The one or more protection circuits 4250 in accordance with the presenttechnology may comprise an electrical protection circuit, a temperatureand/or pressure safety circuit.

5.4.2.7 Memory

In accordance with one form of the present technology, the RPT device4000 includes memory 4260, e.g., non-volatile memory. In some forms,memory 4260 may include battery-powered static RAM. In some forms,memory 4260 may include volatile RAM.

Memory 4260 may be located on the PCBA 4202. Memory 4260 may be in theform of EEPROM or NAND flash.

Additionally or alternatively, RPT device 4000 includes a removable formof memory 4260, for example, a memory card made in accordance with theSecure Digital (SD) standard.

In one form of the present technology, the memory 4260 acts as anon-transitory computer readable storage medium on which is storedcomputer program instructions expressing the one or more methodologiesdescribed herein, such as the one or more algorithms.

5.4.2.8 Data Communication Systems

In one form of the present technology, a data communication interface4280 is provided, and is connected to the central controller 4230. Datacommunication interface 4280 may be connectable to a remote externalcommunication network 4282 and/or a local external communication network4284. The remote external communication network 4282 may be connectableto a remote external device 4286. The local external communicationnetwork 4284 may be connectable to a local external device 4288.

In one form, data communication interface 4280 is part of the centralcontroller 4230. In another form, data communication interface 4280 isseparate from the central controller 4230, and may comprise anintegrated circuit or a processor.

In one form, remote external communication network 4282 is the Internet.The data communication interface 4280 may use wired communication (e.g.,via Ethernet, or optical fibre) or a wireless protocol (e.g., CDMA, GSM,LTE) to connect to the Internet.

In one form, local external communication network 4284 utilises one ormore communication standards, such as Bluetooth, or a consumer infraredprotocol.

In one form, remote external device 4286 is one or more computers, forexample a cluster of networked computers. In one form, remote externaldevice 4286 may be virtual computers, rather than physical computers. Ineither case, such remote external device 4286 may be accessible to anappropriately authorised person such as a clinician.

The local external device 4288 may be a personal computer, mobile phone,tablet or remote control.

5.4.2.9 Output Devices Including Optional Display, Alarms

An output device 4290 in accordance with the present technology may takethe form of one or more of a visual, audio and haptic unit. A visualdisplay may be a Liquid Crystal Display (LCD) or Light Emitting Diode(LED) display.

5.4.2.9.1 Display Driver

A display driver 4292 receives as an input the characters, symbols, orimages intended for display on the display 4294, and converts them tocommands that cause the display 4294 to display those characters,symbols, or images.

5.4.2.9.2 Display

A display 4294 is configured to visually display characters, symbols, orimages in response to commands received from the display driver 4292.For example, the display 4294 may be an eight-segment display, in whichcase the display driver 4292 converts each character or symbol, such asthe figure “0”, to eight logical signals indicating whether the eightrespective segments are to be activated to display a particularcharacter or symbol.

5.5 Humidifier 5.5.1 Humidifier Overview

In one form of the present technology, there is provided a humidifier5000 (e.g., as shown in FIGS. 5a, 5c and 5d ) to change the absolutehumidity of air or gas for delivery to a patient relative to ambientair. Typically, the humidifier 5000 is used to increase the absolutehumidity and increase the temperature of the flow of air (relative toambient air) before delivery to the patient's airways.

The humidifier 5000 may comprise a humidifier reservoir 5110, ahumidifier inlet 5002 to receive a flow of air, and a humidifier outlet5004 to deliver a humidified flow of air. In some forms, as shown inFIG. 5c and FIG. 5d , an inlet and an outlet of the humidifier reservoir5110 may coincide with the humidifier inlet 5002 and the humidifieroutlet 5004 respectively. The humidifier 5000 may further comprise ahumidifier base 5006, which may be adapted to receive the humidifierreservoir 5110 and comprise a heating element 5240.

5.5.2 Humidifier Mechanical Components 5.5.2.1 Humidifier Reservoir

According to one arrangement, the humidifier 5000 may comprise ahumidifier reservoir 5110 configured to hold, or retain, a volume ofliquid (e.g., water) to be evaporated for humidification of the flow ofair. The humidifier reservoir 5110 is typically configured to hold apredetermined maximum volume of water in order to provide adequatehumidification for at least the duration of a respiratory therapysession, such as one evening of sleep. Typically, the reservoir 5110 isconfigured to hold several hundred millilitres of water, e.g., 300millilitres (ml), 325 ml, 350 ml or 400 ml. In other forms, thehumidifier 5000 may be configured to receive a supply of water from anexternal water source such as a building's water supply system.

In one arrangement as shown in FIG. 6, the humidifier reservoir 5110comprises an inlet 5118 configured to receive a flow of air to theinterior of the humidifier reservoir 5110. The humidifier reservoir 5110may be configured so that the flow of air may be further humidified asit passes through the interior of the humidifier reservoir 5110. Thehumidifier reservoir 5110 also comprises an outlet 5122 configured todeliver the humidified flow of air out of the humidifier 5000. Theoutlet 5122 may be connected to an air circuit 4170 through which thehumidified flow of air may be delivered to the patient 1000 via thepatient interface 3000. In one form, the humidifier reservoir 5110 maybe configured to encourage the flow of air to travel in a tortuous paththrough the reservoir 5110 while in contact with the volume of watertherein, in order to maximize the surface area of the water that the aircontacts as it travels between the inlet 5118 and the outlet 5122.

According to one form, the reservoir 5110 may be removable from thehumidifier 5000, for example, in a horizontal direction as shown inFIGS. 5C and 5D.

The reservoir 5110 may also be configured to discourage egress of liquidtherefrom, such as when the reservoir 5110 is displaced and/or rotatedfrom its normal, working orientation, such as through any aperturesand/or in between its sub-components. As the flow of air to behumidified by the humidifier 5000 is typically pressurised, thereservoir 5110 may also be configured to prevent losses in pneumaticpressure through leak and/or flow impedance.

5.5.2.2 Conductive Portion

According to one arrangement, the reservoir 5110 comprises a conductiveportion 5152 configured to allow efficient transfer of heat from theheating element 5240 to the volume of liquid in the reservoir 5110. Inone form, the conductive portion 5152 may be arranged as a plate,although other shapes may also be suitable. All or a part of theconductive portion 5152 may be made of a thermally conductive materialsuch as aluminium (e.g., approximately 2 mm thick, such as 1 mm, 1.5 mm,2.5 mm or 3 mm), another heat conducting metal or some plastics. In somecases, suitable heat conductivity may be achieved with less conductivematerials of suitable geometry.

The conductive portion 5152 may be coupled with a heating element 5240to introduce heat to the interior of the humidifier reservoir 5110.Humidifier reservoir dock

In one form, the humidifier 5000 may comprise a humidifier reservoirdock 5130 (as shown in FIG. 5D) configured to receive the humidifierreservoir 5110. In some arrangements, the humidifier reservoir dock 5130may comprise a locking feature such as a locking lever 5135 configuredto retain the reservoir 5110 in the reservoir dock 5130.

5.5.2.3 Water Level Reference

The humidifier reservoir 5110 may comprise a water level reference 5150as shown in FIG. 5C-5D. In some forms, the water level reference 5150may provide one or more references to a user such as the patient 1000 ora care giver regarding a quantity of the volume of water in thehumidifier reservoir 5110. The one or more references provided by thewater level reference 5150 may include an indication of a maximum,predetermined volume of water, and/or any portions thereof, such as 25%,50% or 75% or volumes such as 200 ml, 300 ml or 400 ml.

5.5.2.4 Heating Plate 5120

According to another aspect of the present technology, the humidifier5000 may comprise a heating plate 5120 that is used to transfer heat tothe humidifier reservoir 5110 as shown in FIG. 6. The heating plate 5120may comprise a heating element 5240 located on or near the base of thehumidifier 5000. In one form, the heating plate 5120 may simply cover aheating element 5240. The heating plate 5120 may be formed, for example,of a nickel chrome alloy, stainless steel or anodised aluminium.

5.5.3 Humidifier Electrical & Thermal Components (FIG. 5B)

The humidifier 5000 may comprise a number of electrical and/or thermalcomponents such as those listed below.

5.5.3.1 Humidifier Sensor(s)

The humidifier 5000 may comprise one or more humidifier sensors (e.g.,transducers) 5202 instead of, or in addition to, sensors 4270 describedabove. Humidifier sensors 5202 may include one or more of a pressuresensor 5205, a flow rate sensor 5210, a temperature sensor 5220, or ahumidity sensor 5218 as shown in FIG. 5B. A humidifier sensor 5202 mayproduce one or more output signals which may be communicated to acontroller such as the central controller 4230 and/or the humidifiercontroller 5250. In some forms, a humidifier sensor may be locatedexternally to the humidifier 5000 (such as in the air circuit 4170)while communicating the output signal to the controller. The term‘sensor’ will be taken to include one or more transducers in the presentdocument unless otherwise explicitly stated. Such an externally locatedsensor can permit implementation of a replaceable humidifier reservoir(e.g., container) that does not also require replacement or removal ofthe sensor (e.g., the sensor is not directly coupled to the container).

5.5.3.1.1 Pressure Sensor

One or more pressure sensors 5205 may be provided to the humidifier 5000in addition to, or instead of, a pressure sensor 4272 provided to theRPT device 4000.

5.5.3.1.2 Flow Rate Sensor

One or more flow rate sensors 5210 may be provided to the humidifier5000 in addition to, or instead of, a flow rate sensor 4274 provided tothe RPT device 4000.

5.5.3.1.3 Temperature Sensor

The humidifier 5000 may comprise one or more temperature sensors 5220.The one or more temperature sensors 5220 may be configured to measureone or more temperatures, such as the temperature of the heating element5240 and/or the temperature of the flow of air through the humidifier(e.g., in the humidifier 5000 and/or downstream of the humidifier outlet5004). In some forms, the humidifier 5000 may further comprise atemperature sensor 5220 configured to detect the temperature of theambient air.

5.5.3.1.4 Humidity Sensor

In one form, the humidifier 5000 may comprise one or more humiditysensors 5218 to detect a humidity of a gas, such as the ambient air. Ahumidity sensor 5218 may be placed near the humidifier outlet 5004 insome forms to measure a humidity of the gas delivered out of thehumidifier 5000. Each humidity sensor may be an absolute humidity sensoror a relative humidity sensor.

5.5.3.2 Heating Element

A heating element 5240 may be provided to the humidifier 5000 in orderto provide a heat input to liquid and/or gas therein. For example, theheating element 5240 may provide a heat input to one or more of: thevolume of water in the humidifier reservoir 5110; and the flow of airthrough the humidifier. The heating element 5240 may comprise a heatgenerating component such as an electrically resistive heating track.One suitable example of a heating element 5240 is a layered heatingelement such as one described in the PCT Patent Application PublicationNo. WO 2012/171072, which is incorporated herewith by reference in itsentirety.

In some forms, the heating element 5240 may be provided in thehumidifier base 5006 where heat may be provided to the humidifierreservoir 5110 primarily by conduction as shown in FIG. 5D. According toone arrangement, the heating element 5240 may be moulded into a resinforming a tub, as disclosed in the PCT patent application WO2008/148154, the contents of which is incorporated herein by reference.

5.5.3.3 Humidifier Controller

According to one arrangement of the present technology, a humidifier5000 may comprise a humidifier controller 5250. In one form, thehumidifier controller 5250 may be a part of the central controller 4230.In another form, the humidifier controller 5250 may be a separatecontroller, which may be in communication with the central controller4230 as shown in FIG. 4C.

In one form, the humidifier controller 5250 may receive as inputsmeasurements of properties (such as temperature, humidity, pressureand/or flow rate), for example, of the flow of air, and/or of the waterin the reservoir 5110 and/or the humidifier 5000. The humidifiercontroller 5250 may also be configured to execute or implementhumidifier algorithms and/or deliver one or more output signals.

As shown in FIG. 5B, the humidifier controller may comprise one or morecontrollers, such as a central humidifier controller 5251, a heated aircircuit controller 5254 configured to control the temperature of aheated air circuit 4170, and/or a heating element controller 5252configured to control the temperature of a heating element 5240. In somecases, humidifier algorithms may also utilize outputs from one or moresensors.

5.5.3.4 Water Quantity (Level/Volume) Determination

As discussed in further detail above, the humidifier reservoir 5110 maycontain a body of liquid, such as water, which is evaporated to addhumidity to the flow of air travelling through the humidifier 5000. Insome cases, it may be desirable to determine the quantity of liquid thatis present in a humidifier reservoir 5110. It is noted that wherereferences are made to determination of ‘water quantity’, it is to beunderstood that such techniques are not to be limited to applications indetermining a quantity of water, but would also be applicable to otherliquids. It may be desirable for the humidifier 5000 to self-monitor thequantity of water in the reservoir 5110 without active monitoring by auser/person. For example, if the user is visually impaired orincapacitated, the user may be unable to visually inspect the quantityof water in the reservoir 5110. Also, it may be difficult for a user todetermine the height of water in the reservoir 5110 if the reservoir isopaque, or if the room where the humidifier 5000 is located is darkenedfor the user to relax or eventually sleep.

In some forms, it may be desirable to determine the quantity of water inthe reservoir 5110 by indirect measurements, such as without sensing awater level by detecting its height with a mechanical float. Forexample, indirect measurements of the quantity of water may allowdetermination of the water quantity without use of sensors that form apart of a disposable component such as the reservoir 5110. Furthermore,indirect measurements of the quantity of water may be carried out usingsensors that may have other functions, such as control of temperatureand/or pressure (e.g., therapy pressure) of the air flow delivered tothe patient, which may lead to improved efficiency and/or lower cost.Indirect measurements of water quantity are described in further detailbelow. Thus, in some cases, a dedicated sensor(s) may be implemented forthe detection of water quantity. However, in some cases, the sensor(s)involved in other standard control functions of an RPT device (e.g.,pressure control or flow sensing etc.) may be additionally tasked toserve the different purpose of water quantity sensing.

The quantity of water may be determined and/or processed in terms of anynumber of units, relative or absolute. For example, the quantity ofwater may be measured in a unit of volume, such as litres, millilitresor cubic centimeters, in a unit of mass such as in grams, kilograms orounces, in relative measurements such as a percentage or a fraction ofthe maximum recommended fill level, in any arbitrary units such as anumber out of five or a number out of 10, where the maximum numberrepresents the maximum recommended fill level, and in some cases by ameasurement of the size of the void (e.g., the quantity of air) in thereservoir 5110. In some forms, the water quantity may be expressed as a‘level’ to indicate a height, however it will be understood that areference to any particular form of measurement (e.g., water level,water volume or water mass) is not intended to be limiting to theexpress form. Thus, in some cases the determined reservoir waterquantity may be expressed as an amount of water needed to fill thehumidifier given the amount of water present in the humidifier or it maybe expressed as the amount of water present in the humidifier.

5.5.3.4.1 Use of Determined Water Quantity

One advantage associated with being able to determine the quantity ofwater present in the reservoir 5110 may be in being able to inform, oralert a user, such as a caregiver or a patient 1000, of the determinedwater quantity. Additionally, or alternatively, the user may be informedor alerted based on other information which may be inferred from thedetermined water quantity. According to one aspect of the presenttechnology, the patient 1000 may be alerted of a low water quantityprior to commencement of a therapy session. For example, the patient maybe alerted if the determined water quantity is below a predeterminedthreshold level. In some cases, the alert may identify by estimate ofhow much time or number of sessions of use of the RPT will remain beforeadditional water will be needed. Such an estimate may be based onhistoric water depletion data (e.g., recorded time of use and quantityof water depleted, rate of water depletion, etc.) given a patient's RPTuse.

According to another such aspect, a controller may determine whether thedetermined water quantity may be sufficient for humidification of airflow throughout a remainder of a therapy session. In one form, the usermay be prompted to refill the reservoir 5110 before commencing therapy.In one form, the user may be alerted upon completion of therapy torefill the reservoir 5110 if the determined water quantity may not besufficient for humidification of air throughout the entirety of anothertherapy session.

According to another aspect, an alarm may be activated when thereservoir 5110 is out of water, or when the water level is determined tobe low (e.g., below a threshold). An alarm may be activated at any time,such as prior to commencement of a therapy session, at the completion ofa therapy session, or during a therapy session. In one form, acontroller such as a central controller 4230 or the humidifiercontroller 5250 may activate an alarm. In some cases where the patient1000 requires humidified air and may not be able to refill the reservoir5110 without assistance, the alarm may alert a caregiver (e.g., a nurse)that refilling is required, such as by transmission of an alert messagevia a communications device (e.g., email, pager message, short messageservice (SMS) message, etc.).

In another form, determination of water quantity in the reservoir 5110may allow for a humidification output to adapt to the available waterquantity and/or the rate of water usage, as will be described below infurther detail.

In some arrangements, the reservoir 5110 may be disposable and mayrequire replacement (e.g., periodically, based on usage or forindividual patients) throughout a life of the humidifier 5000. In sucharrangements, the introduction of any additional components into thereservoir 5110, such as a sensor, may not be desirable, as this mayincrease the cost of the disposable reservoir 5110, particularly if theadditional components are relatively expensive. Yet further, in order tointroduce a sensor into the reservoir 5110, which may be removable fromthe humidifier 5000, one or more electrical connections that can becoupled and uncoupled may be required between the humidifier reservoir5110 and other components such as the humidifier controller 5250 and/ora power source (e.g., power supply 4210). The presence of suchelectrical connections that can be coupled and uncoupled may also not bepreferable, as they may increase system complexity, increase the cost ofthe disposable reservoir 5110, and introduce potential failure points ina disposable component.

Thus, it may be preferable to determine a quantity of water in ahumidifier reservoir 5110 using one or more sensors that do not form apart of the reservoir 5110 (i.e., not a component of thedisposable/replaceable portion of the humidifier system). Furthermore,it may be preferable to determine the water quantity using the sensorsthat may also be used in a humidifier 5000 and/or an RPT device 4000,for example, to measure one or more properties of the air flow.

5.5.3.4.2 Determination of Effects of Varying Water Quantity

According to some arrangements of the humidifier reservoir 5110according to the present technology, a variation in the quantity ofwater present in the humidifier reservoir 5110 may affect one or moremeasurable characteristics or properties, such as those of: the water,the flow of air, the reservoir 5110 and/or the humidifier 5000. Thecharacteristic(s) or property(s) affected by a variation in the quantityof water (and thus may be used to infer the quantity of water) mayinclude, but not be limited to, pressure, flow rate, noise, temperatureor vibration. These characteristics will be referred to hereafter asindicative characteristics. A person skilled in the art would understandgiven the present specification that there may be other, similar,characteristics to those ‘indicative characteristics’ disclosed in thepresent document, which may also be used to determine a water quantityin the reservoir 5110 in a manner substantially equivalent to thosedisclosed herewithin.

Thus, one or more measurements of one or more indicative characteristicsmay be used to determine the quantity of water in the reservoir 5110. Aquantity of water may be determined for a particular time, or a changein the quantity of water in the reservoir 5110 between a first time anda second time may be determined. For example, a measurement of theindicative characteristic may be used as a variable in a look-up tableor in a function to determine an estimate of the quantity of water inthe reservoir 5110 or the change in the quantity of water in thereservoir 5110 between two points in time.

As will be described in further detail below, a measurement of anindicative characteristic may be a measurement of an aspect of theindicative characteristic, such as a magnitude or a direction of avector quantity. For example, where a noise is an indicativecharacteristic, a measurement of an indicative characteristic may be ameasurement of amplitude of the noise, a measurement of phase of thenoise, or a combination of both aspects.

In some forms, each ‘measurement’ herein may in fact refer to a set ofmeasurements (one or more measurements or values derived from one ormore sensors), such that for example a first set of measurements and asecond set of measurements may be used to determine the quantity ofwater.

In one form, a plurality of measurements such as a first measurement anda second measurement of the indicative characteristic(s) may be used todetermine the quantity of water. The plurality of measurements may be ofone indicative characteristic or a plurality of indicativecharacteristics. For example, a measurement of pressure of the flow ofair from a pressure sensor and a measurement of flow rate of the flow ofair from a flow rate sensor may be used to determine the quantity ofwater.

The plurality of measurements may be obtained from a single sensor, or aplurality of sensors. As an example, a first microphone may measure afirst measurement of noise and a second measurement of noise. Or, afirst microphone and a second microphone may respectively measure afirst measurement of noise and a second measurement of noise. The firstmeasurement of noise and the second measurement of noise may then beused to determine the quantity of water in the reservoir. In anotherform, one measurement of an indicative characteristic may be used todetermine the water quantity in the reservoir 5110. For example, asingle measurement of noise from a microphone may be used to determinethe quantity of water.

The measurement system may generate a reference signal such as awaveform (e.g., with a predetermined shape, frequency and/or amplitude),or an impulse, for use in determination of water quantity. To this end,the measurement system may comprise a reference generator configured togenerate the reference signal, such as a loudspeaker or the blower 4142.In some forms, the reference signal may be measured by one or moresensors to determine a reference data set, to which a measurement setmay be compared to determine a quantity of water. A measurement set maybe determined (e.g., second measurement set measured) after at least apredetermined length of time has passed subsequent to the reference dataset (e.g., first measurement set).

In some forms, the reference data set may be determined from estimation,whereby water quantity may be determined from a resulting measurementset (e.g., from a single sensor 5202-3 as shown in FIG. 9) and theestimated reference data set. For example, a reference data set mayinclude an estimated pressure based on a measurement of motor speed. Inone form, a time taken for a reference signal (e.g., airflow, sound ornoise) to travel from the reference generator, through the reservoir5110, and to the sensor may be measured to determine a time lag. Yetfurther, any transformation, such as a phase change, or a change inamplitude, that the reference signal undergoes prior to arriving at thesensor, may then be measured and used to infer the volume of water inthe reservoir 5110.

Further details of determination of the quantity of water in thereservoir 5110 by use of indicative characteristics will be discussedbelow.

5.5.3.4.3 Measurements of the Air Flow

According to one aspect of the present technology, a quantity of waterin the reservoir 5110 may be determined from a measurement set (one ormore measurements) of the air flow, for example as measured in thereservoir 5110 or downstream of the reservoir 5110. As used herein, ameasurement or a measurement set may comprise a single measured valuefrom a sensor, or a plurality of measured values from a sensor. In oneexample, a plurality of measured values from a sensor may be averagedover a short period of time to determine an average value of aparticular characteristic over the short period of time. In such anexample, by averaging a plurality of measured values from a singlesensor, the measurement from the sensor may be used to more accuratelydetermine the water volume in the reservoir 5110, such as if, forexample, a user accidently jostles the reservoir 5110 during sensing ofthe values from the sensor. In another example, a plurality of measuredvalues from a sensor may be filtered (e.g., using a low-pass signalfilter) to determine a representative value of a particularcharacteristic over a period of time.

A property of the reservoir 5110 and the water contained therein, suchas its acoustic transmission loss, flow impedance, thermal mass orthermal conductivity, may vary according to the quantity of waterpresent in the reservoir 5110. In turn, one or more characteristics ofthe flow of air that travels through the reservoir 5110 may be affected,such as pressure, flow rate, temperature, noise, or vibration. Thus, theaffected characteristic(s) of the air flow may indicate the quantity ofwater in the reservoir 5110 when measured in the reservoir 5110 ordownstream of the reservoir 5110, and in some cases, when measuredupstream of the reservoir 5110. For example, a decrease in the quantityof water in the reservoir 5110 may decrease the overall thermal mass ofthe reservoir 5110.

FIG. 6 shows an arrangement of a system according to the presenttechnology that comprises a first sensor 5202-1 and a second sensor5202-2. Three exemplary, possible quantities of water in the reservoir5110 are indicated by three water levels WL-1, WL-2 and WL-3 in FIG. 6.An exemplary travel path for the flow of air through the reservoir 5110is indicated by the arrows AF.

The flow of air may undergo a pressure drop (e.g., a decrease in staticor total pressure) as it travels through the reservoir 5110, forexample, as measured between the reservoir inlet 5118 and the reservoiroutlet 5122. A magnitude of the drop in pressure of the flow of air mayvary according to a flow impedance of the reservoir 5110. As thequantity of water in the reservoir 5110 is varied, the flow impedance ofthe reservoir 5110 may be altered due to a change in a path for the airflow through the reservoir 5110 as the effective boundaries of thereservoir 5110 change (e.g., from WL-1 to WL-2 in FIG. 6). As a result,a difference between the air pressure at the reservoir inlet 5118 and atthe reservoir outlet 5122 may be affected by the change in the quantityof water in the reservoir 5110. Thus a pressure of the flow of air maybe a suitable indicative characteristic of the quantity of water presentin the reservoir 5110.

Similarly, any number of properties of the flow of air may be suitableindicative characteristics of the quantity of water present in thereservoir 5110. Suitable indicative characteristics of the flow of airmay include pressure, flow rate, temperature, density, noise orvibration or other characteristics of the flow of air. Thus, one or moreof the indicative characteristics may be measured from the air flow todetermine the quantity of water in the reservoir 5110.

According to the arrangement shown in FIG. 6, the first sensor 5202-1may determine a first measurement set M1 of an indicative characteristicof the flow of air, and the second sensor 5202-2 may determine a secondmeasurement set M2 of an indicative characteristic the flow of air. Thefirst measurement set M1 and the second measurement set M2, and/or theirrelationship, such as a difference in amplitude, or a difference inphase, may then be correlated to a quantity of water in the reservoir5110 using a function or a look-up table, as will be discussed in moredetail below.

Locations of the sensor(s) need not be limited to the particularexemplary locations discussed herein in order to take advantage of thepresent technology as disclosed. Examples of suitable locations for thesensor(s) may include the inlet or the outlet of the RPT device 4000,the inlet or the outlet of the humidifier 5000, the interior of thereservoir 5110, the interior of the air circuit 4170, the interior ofthe patient interface 3000, or other locations in fluid communicationwith the flow of air. In some cases, the sensor(s) may be locatedbetween or near any of the above listed components. In one arrangement,at least a part of the reservoir 5110 is located between at least twosensors when a plurality of sensors is employed.

Referring to FIG. 6, the first sensor 5202-1 is shown at a firstlocation, upstream of the reservoir 5110, and the second sensor 5202-2is shown at a second location, downstream of the reservoir 5110.Alternatively, the sensors 5202-1 and/or 5202-2 may be arranged as shownin FIG. 6C, where the first sensor 5202-1 is located within thereservoir 5110 and the second sensor 5202-2 is located proximal to thepatient interface 3000. A sensor may be integrally formed with anothercomponent such as the RPT device 4000, an air circuit 4170 or thehumidifier 5000 (or a sub-component thereof). In other arrangements, asensor may be removably connected to another component.

In an arrangement of the present technology as shown in FIG. 6A, a firstpressure sensor 5205-1 and a second pressure sensor 5205-2 may eachdetermine measurements of pressure of the flow of air. The firstpressure sensor 5205-1 may determine a first measurement of pressureP_(m) 1 of the flow of air at a first location, and the second pressuresensor 5205-2 may determine a second measurement of pressure P_(m) 2 ofthe flow of air at a second location. A measurement of pressure dropΔP_(m) between the first location and the second location may bedetermined using the formula ΔP_(m)=P_(m) 1-P_(m) 2. The measurement ofpressure drop ΔP_(m) may then be used to determine the quantity of waterin the reservoir (e.g., as shown in FIG. 7) as described in furtherdetail below.

In an illustrative example, a maximum allowable quantity (in volume) ofwater in the reservoir 5110 may be approximately 350 ml. In FIG. 6, thecorresponding water level may be WL-1. When the water volume is 350 ml,at a therapy pressure (i.e., a pressure at the patient interface 3000)of 10 cm H₂O, a first measurement of pressure P_(m) 1 at the firstpressure sensor 5205-1 may be called P_(m) 1 ₃₅₀ and a secondmeasurement of pressure P_(m) 2 at the second pressure sensor 5205-2 maybe called P_(m) 2 ₃₅₀. Based on the first measurement of pressure P_(m)1 ₃₅₀ and the second measurement of pressure P_(m) 2 ₃₅₀, a measurementof pressure drop at 350 ml of water ΔP_(m350) may be calculated usingthe following formula ΔP_(m350)=P_(m) 1 ₃₅₀−P_(m) 2 ₃₅₀. However, if thewater volume was to decrease to 240 ml for instance, it may lower thewater level to WL-2, increasing the effective internal volume of air inthe reservoir 5110. In this case, the measurement of pressure drop maychange to ΔP_(m240), and similarly at 130 ml of water volume at waterlevel WL-3, the measurement of pressure drop may then change further toΔP_(m130). Thus the quantity of water may be determined based on themeasurement of pressure drop.

In some forms, the quantity of water in the reservoir may be determinedbased on the measurement of pressure drop ΔP_(m), using one or morefunctions and/or look-up tables. An example of a look-up table is shownin FIG. 7, where a series of pressure drop values (measured in pressure)are correlated (such as by numerical, experimentation or empiricalanalysis) to water quantity values (measured in volume). According toone arrangement, a memory 4260, in communication with the controller,may store the data of the look-up tables (and/or functions). Thecontroller may receive the measurement of pressure drop ΔP_(m) as aninput and determine the water quantity based on the look-up table(and/or functions). In one example, the look-up tables may be customizedor adapted by a calibration and/or self-learning process of a controllerof humidifier 5000. For example, different fluid levels may beidentified by a user in response to a prompt of the controller andpressure drops (or other values) may be calculated and associated withthe identified levels.

In some forms, the controller may be configured to determine the waterquantity from the closest value of pressure drop available ΔP in thelook-up table to the measurement of pressure drop ΔP_(m). For instance,in the look-up table shown in FIG. 7, the closest pressure drop value ΔPto the measured pressure drop at 350 ml of water ΔP_(m350) may beΔP_350, and the determined water volume may be 350 ml. Or, the closestpressure drop value ΔP to the measured pressure drop at 240 ml of waterΔP_(m240) may be ΔP_250, and the determined water volume may be 250 mlAlternatively, the controller may be configured to interpolate betweenlisted values in the look-up table by any suitable interpolation methodssuch as linear, polynomial, piecewise constant interpolation or acombination thereof. Using interpolation, two closest values of pressuredrop ΔP to the measured pressure drop at 240 ml of water ΔP_(m240) maybe ΔP_250 and ΔP_225, and the controller may determine the quantity ofwater by interpolating between the two values.

In one form, a look-up table may be multi-dimensional as shown in FIG.8. This may allow effects of any one or more additional variables (suchas therapy pressure (P_(therapy)), pressure at pressure generator,pressure generator motor speed, pressure generator motor current, flowrate, length of air circuit 4170, type of humidifier reservoir 5110 orother indicative characteristics) to be taken into consideration whendetermining the water quantity.

In one form, the look-up table may be populated by a manufacturer bycharacterisation of the reservoir 5110 and stored in a memory (e.g., inthe RPT device 4000 or humidifier 5000). Additionally, or alternatively,the humidifier controller 5250 may also comprise the ability tocalibrate and populate the look-up table by using a learn mode duringtherapy, and/or by executing or performing a calibration cycle, both ofwhich will be described in further detail below.

In one form, the quantity of water may be determined from measurementsof indicative characteristic(s) based on one or more functions. The oneor more functions may be predetermined and made available to acontroller such as the humidifier controller 5250, for example stored ina memory (e.g., in the RPT device 4000 or humidifier 5000). In someforms, the function correlating the indicative characteristic(s) to thequantity of water may be selected from a plurality of functions, forexample, according to a variable (e.g., therapy pressure).Alternatively, or additionally, the function may be calibrated by alearn mode during therapy or by performing a calibration cycle. Thus, inone example, the function may determine the quantity of water, in volumeV_(w) based on a measurement of the pressure drop ΔP_(m), using a linearequation V_(w)=A×ΔP_(m)+B, where A and B are values that may bepredetermined and/or adjusted by calibration/learn mode. The functionmay also take one or more of any number of suitable forms, such as alinear, polynomial, logarithmic or a combination thereof.

FIG. 9 shows an arrangement of a system that comprises a sensor 5202-3.In this arrangement, a measurement M3 determined by the sensor 5202-3may be used as an input to a look-up table or a function to determinethe quantity of water in the reservoir 5110. In another example, areference value M_(ref) may be used to compare to the output or themeasurement M3 produced by the sensor 5202-3 to determine the quantityof water. The reference value M_(ref) may be a fixed and/or apredetermined value. The reference value M_(ref) may additionally oralternatively be determined from another characteristic such as a motorspeed, motor current, ambient temperature, ambient pressure or ambientdensity among others. For example, density of the air through the devicemay be measured, from which temperature of the air may be inferred, fromwhich temperature of the water may be inferred and from which a volumeof water or the reservoir may be estimated. Yet further, the referencevalue M_(ref) may be based at least partly on a previous measurementdetermined by the sensor 5202-3.

In the exemplary arrangement shown in FIG. 9A, a pressure sensor 5205-3is located downstream of the humidifier reservoir 5110, and the pressuresensor 5205-3 may determine a measurement of pressure P_(m) 3. Themeasurement of pressure P_(m) 3 may be used as an input to a look-uptable or a function to determine the quantity of water. Alternatively,or additionally, the measurement of pressure P_(m) 3 may be compared toa reference pressure P_(ref), for example to produce an estimatedpressure drop ΔP_(e)=P_(ref)−P_(m) 3 (where P_(ref) is upstream of P_(m)3). A look-up table or a function may be used to determine the quantityof water based on the estimated pressure drop similarly to the methoddescribed above. The reference pressure may be predetermined, orvariable, for example the reference pressure may be estimated fromparameters such as motor current, motor speed, motor acceleration and/oraltitude as disclosed in PCT Application Number PCT/AU2013/000695 forexample, the entire contents of which is enclosed herewithin byreference. In a yet another alternative, the measurement of pressureP_(m) 3 may be used as an input to a look-up table or a function,wherein the look-up table or the function may vary according to thereference pressure P_(ref).

In some forms, the quantity of water in the reservoir 5110 may bedetermined from a plurality of measurements of indicativecharacteristics over time. For example, measurements of indicativecharacteristics over time may include effects of one or more breathwaveforms, such as inspiratory or expiratory waveforms. Characteristicsof the flow of air such as its pressure, flow rate or temperature may beaffected due to breathing of the patient 1000. For example, when thepatient 1000 breathes out, the air pressure may increase, including ator near the humidifier reservoir 5110. When the patient 1000 breathesin, the air pressure may decrease, including at or near the humidifierreservoir 5110. A magnitude of a variation of the indicativecharacteristics (such as pressure) may depend on a quantity of water inthe reservoir 5110. The effect that the patient's breathing has to thecharacteristics of the flow of air may thus be measured to determine thequantity of water in the reservoir 5110. In some cases, detection ofpatient breathing cycle, e.g., expiration, inspiration or parts thereof,may trigger timing of particular measurements for water level detection.For example, a measurement may be synchronized for a particular phase ofthe patient's respiratory cycle (such as the start of expiration or thestart of inspiration) so as to assist with controlling for changes tothe system that may be influenced by the patient's breathing cycle.

In another example, one or more of a patient's breath waveforms (or apart thereof), such as inspiratory or expiratory waveforms may bedetermined using an arrangement as shown in FIG. 9B. For instance, adifference in flow rates between expiration and inspiration at a flowrate sensor 5210-3 may be determined by producing a measurement ofmaximum flow rate and a measurement of minimum flow rate over a breathcycle. The difference in flow rates may then be calculated as thedifference between the measurement of maximum flow rate and themeasurement of minimum flow rate over a breath cycle. The water levelmay then be determined by correlation to, for example, the differencebetween flow rate between expiration and inspiration.

In one arrangement of the present technology, the central controller4230 of the RPT device 4000 may be configured to maintain the blower4142 at a fixed speed for each target therapy pressure. According tothis arrangement, a change in flow impedance of the reservoir 5110 mayaffect the flow rate of air through the air circuit, as the blower 4142operates at a constant speed.

FIG. 9B shows one arrangement of a system that may be suitable fordetermining the quantity of liquid in the reservoir 5110 using a flowrate sensor 5210-3 when such a constant-speed blower is used. The flowrate sensor 5210-3 may produce a measurement of the flow rate F_(m) 3,which would vary as the flow impedance of the reservoir 5110 varies.Accordingly, the measurement of the flow rate F_(m) 3, as well as aspeed of the blower 4142 may be correlated to determine the quantity ofwater in the reservoir 5110, such as, by using a two-dimensional look-uptable or a two-variable function. In some cases, other characteristics,such as motor current or altitude may be added as independent dimensionsor variables to the look-up table and/or the function to further improveaccuracy of the look-up table of the function.

According to a yet another aspect of the present technology, noise maybe a suitable indicative characteristic from which the quantity of watermay be determined. For example, a sensor may be placed to determine ameasurement of noise at a location where the noise may be affected bythe quantity of water in the reservoir 5110. Suitable locations mayinclude: in the reservoir 5110 or downstream of the reservoir 5110 suchas in the humidifier 5000, in the air circuit 4170 or the patientinterface 3000. The resulting noise may be used to determine thequantity of water remaining in the reservoir 5110, for example by acomparison to a measured or estimated reference noise.

In some cases, the reference noise may be a noise output by a referencegenerator, which may be a component of the RPT device 4000 and/or thehumidifier 5000. For example, noise created by the blower 4142 as aby-product of generating a pressured flow of air may be used as thereference noise. In this case, the level and frequency characteristicsof the reference noise may therefore vary (e.g., according to a pressureor flow rate delivered by the blower 4142), and may need to be measured(or estimated) in conjunction with the resulting noise to establish arelationship therebetween. Alternatively, or additionally, the referencenoise input may include a known noise output from a component such as aspeaker or a buzzer. According to another feature of the presenttechnology, the measurement of the resulting noise may include a filterto exclude or reduce the effects of other noise sources, such as snoringby the patient 1000 or background noise near the patient 1000.

According to an exemplary arrangement shown in FIG. 6B, a firstmicrophone 5215-1 may be placed upstream of the reservoir 5110 tomeasure a reference noise, and a second microphone 5215-2 may be placeddownstream of the reservoir 5110 to measure a resulting noise. Thereference noise and resulting noise measurements may be correlated to awater quantity by, for example, calculating the attenuation in noiselevels between the first microphone 5215-1 and the second microphone5215-2. The attenuation in noise levels may be correlated to a quantityof water using similar methods to those described above (e.g., via alook-up table or a function).

Alternatively, in some forms, the reference noise may be estimated(e.g., according to another measure) rather than measured. In oneexample, where the reference noise includes a known noise output (e.g.,from a component such as speaker or a buzzer) the reference noise may beestimated as a predetermined noise. In some forms, the reference noisemay be estimated based on another parameter such as motor speed or motorcurrent. For example, a noise output of a RPT device 4000 and/or ahumidifier 5000 or a component thereof (e.g., of the blower 4142) may becharacterized by its manufacturer, from which a predetermined look-uptable of reference noise may be saved onto a memory of the RPT device4000 and/or a humidifier 5000.

In an arrangement shown in FIG. 9C, one or more measurements from amicrophone 5215-3 may be used to determine the water quantity in thereservoir 5110. The microphone 5215-3 may produce a measurement of theresulting noise level N_(m) 3, which may be used to determine the waterquantity in this case using a look-up table or a function. In oneexample, a function may use as inputs the resulting noise level N_(m) 3,as well as a predetermined reference noise to output (i.e., determine)the water quantity. In another example, a look-up table may bemulti-dimensional, such that a look-up table may receive as inputs amotor speed, and the resulting noise level N_(m) 3 to determine thewater quantity.

Noise may be characterised in a number of ways, for example by a noiselevel (indicating amplitude, typically expressed in decibels or dB), asdescribed above. Alternatively, or additionally, noise may becharacterised by frequency domain data. For example, noise may becharacterised such that for a noise level may be measured for one ormore of a plurality of frequencies (or frequency bands). In thearrangement shown in FIG. 6B, a first noise spectrum may be determinedat the first sensor 5215-1 and compared to a second noise spectrumdetermined at the second sensor 5215-2. Such a comparison may indicatehow the first noise spectrum correlates to the second noise spectrum.For example, the comparison may evaluate changes in noise levels at afrequency and/or a frequency band in the first noise spectrum to thesecond noise spectrum. In one form, the first noise spectrum may becompared to a second noise spectrum, for example to determine a noiseattenuation spectrum for correlation to a water quantity.

Measurements of noise may not be limited to those of audible frequencyranges. In some forms, measurements of inaudible vibrations of the flowof air, such as ultrasounds, may be used to determine a quantity ofwater in the reservoir 5110.

In another aspect of the present invention, a time lag between twolocations in the pneumatic path may be used to determine the quantity ofwater. A change to the quantity of water in the reservoir 5110 mayaffect a length of time taken for the flow of air to travel through thehumidifier reservoir 5110. Accordingly, the length of time taken, or thetime lag, for the flow of air to travel through the humidifier reservoir5110 may be correlated to the quantity of water in the reservoir 5110 byway of a look-up table or a function similarly to those described above.

FIG. 6 shows an exemplary arrangement of the present technology suitablefor determining a time lag between two locations. In the arrangementshown in FIG. 6, the first sensor 5202-1 may determine a referencemeasure set, which may be a plurality (e.g., a series) of measurementsor a single measure of the flow of air, where the reference measure isassociated with a first time T₁ (e.g., a time at the start of the end ofthe reference measure). The second sensor 5202-2 may measure a resultingmeasure set associated with a second time T₂, wherein the resultingmeasure set correlates to the reference measure set. A difference intime ΔT may be determined (e.g., using an equation ΔT=T₂−T₁) and may becorrelated to the quantity of water. In some forms, where the resultingmeasure set and the reference measure set each comprise a waveform(e.g., a plurality of measurements made over a time period), the twowaveforms may be compared for equivalence in the waveform shape todetermine that the resulting measure correlates to the referencemeasure.

The determination of water quantity using any of the above methods maybe made using a look-up table or a function. The particular look-uptable and/or the function may vary between implementations of thepresent technology as the correlation may vary for a number of factors,for example locations of the sensor(s) or the geometry of the humidifier5000. The number of variables used to create the look-up table and/orthe function may be varied while taking advantage of the presenttechnology. For example, as described above, introducing additionalvariables may improve the accuracy of the look-up table and/or thefunction, however in some forms, a look-up table or a function that usesone or two indicative characteristics as variables may be utilised.

It should be noted that the number of sensors employed towardsdetermination of water quantity may be varied from the specific examplesdisclosed herewithin while still taking advantage of the presenttechnology. In some cases, a pre-therapy and/or a post-therapy processmay be executed by the controller to make the above measurements fordetection of a correlated water quantity to determine water quantity byany of the methodologies described herein. However, in some cases such aprocess may be made periodically or continuously during a therapysession.

5.5.3.4.4 Measurements of the Humidifier 5000

According to another aspect of the present technology, the quantity ofwater in the reservoir 5110 may be determined from one or moremeasurements of characteristics of the humidifier 5000, such as itsvibratory characteristics or mechanical characteristics.

5.5.3.4.4.1 Vibration

As the quantity of water in the reservoir 5110 varies, vibrationcharacteristics of the reservoir 5110, and/or the humidifier 5000 mayvary accordingly. For example, vibratory characteristics such as thedamping ratio, natural frequencies and/or transmission loss of an objector a system (e.g., humidifier reservoir 5110 or humidifier 5000) maydepend on one or more aspects of the object or the system, for example,the mass, density, material damping rate or stiffness among others.Further examples of vibration characteristics that may be affectedinclude vibration attenuation through the humidifier reservoir 5110(overall or depending on frequency), and natural vibration frequenciesof the reservoir 5110. Thus one or more measurements of vibrationcharacteristics (e.g., of the reservoir 5110 and/or the humidifier 5000)may be used to determine a quantity of water in the reservoir 5110, suchas by correlating any of these characteristics with water quantities.

Vibration characteristics of the humidifier reservoir 5110 may bedetermined by one or more of a number of ways known to those skilled inthe art. In one example, a measurement of vibration response may becompared against a vibration reference to determine vibrationcharacteristics of the humidifier reservoir 5110.

According to one exemplary arrangement as shown in FIG. 10, a vibrationsource 5232 located on, for example, the RPT device 4000 and/or thehumidifier 5000 may be configured to provide a reference vibration inputsuch as a vibration impulse of a predetermined magnitude or a periodicvibration to the humidifier reservoir 5110. In some forms, a vibrationsource 5232 may provide a varying reference vibration input, for examplewhere the blower 4142 is used as a vibration source 5232. A referencevibration from the blower 4142 may vary for example according to apressure and/or flow rate delivered by the blower 4142. The referencevibration input may be, for example, in an audible frequency range, oran inaudible frequency range (i.e., subsonic or ultrasonic). Thereference vibration input may also be predominantly transmitted to thereservoir 5110 via a gas, liquid, solid or any combination thereof, suchas the flow of air, the water, or the structure of, for example, the RPTdevice 4000 and/or the humidifier 5000.

A vibration sensor 5234 as shown in FIG. 10 may be used to produce ameasurement of a vibration response, for example of the humidifierreservoir 5110, including the water contained therein. A suitableexample of a vibration sensor 5234 may be a piezoelectric accelerometeror a velocity sensor. The measurement of the vibration response may thenbe used to determine the quantity of water in the reservoir 5110. Forinstance, a natural frequency of the reservoir 5110 may typicallyincrease as a quantity of water is reduced in the reservoir 5110, andmay typically decrease as a quantity of water increases.

Alternatively, or additionally, a plurality of measurements ofvibrations may be used to determine the quantity of water. For example,vibration may be measured at a plurality of locations, wherein thereservoir 5110 is located at least partially therebetween the twolocations. A difference in the two measurements of vibration may be alsoreferred to as vibration attenuation, and may depend on a quantity ofwater in the reservoir 5110. Thus a measurement of any number ofvibration characteristics, such as the natural frequency of thereservoir, the overall magnitude of vibration at the reservoir 5110, orthe vibration attenuation between the vibration reference and at thereservoir 5110 may also be used (e.g., by correlation) to determine thequantity of water.

As previously discussed, it may be preferable to arrange any sensors orsensors to be discrete from a disposable component such as the reservoir5110. Therefore, in some forms, the vibration sensor 5234 may beremovably coupled to the reservoir 5110 to measure its vibrationcharacteristic(s), or measure vibration characteristic(s) of thereservoir 5110 indirectly. Thus, in one form, the vibration sensor 5234may be configured to determine vibration characteristics of thereservoir 5110 such as by measuring a vibration response of thehumidifier 5000.

5.5.3.4.4.2 Mechanical

In another aspect of the present technology, a mechanical property or amechanical response of the humidifier 5000 and/or the reservoir 5110 maybe measured to determine the quantity of water in the reservoir 5110.

According to one arrangement, a strain sensor/gauge (or a deformationsensor) may be placed at a base of the humidifier reservoir 5110 tomeasure a strain (or deformation) of a base of the reservoir 5110 due tothe weight of the water therein, for example. The deformation of thebase of the humidifier reservoir 5110 may be dependent on the quantityof water, thus the measurement of the deformation or strain may becorrelated to determine to the quantity of water in the reservoir 5110.Alternatively, or additionally, the strain sensor may also be located ata number of other locations such as the side of the reservoir 5110, oron humidifier 5000 where it may be deformed according to a varyingquantity of water in the reservoir 5110. Any number of other sensorssuch as tilt sensors or load cells may also produce a measurement thatmay be suitable indicative characteristics of the quantity of water. Yetfurther, similarly to above, a look-up table or a function may be usedto determine the quantity of water from the measurement of themechanical property produced by a sensor.

5.5.3.4.5 Measurements of Inertial Mass

According to another aspect of the present technology, the quantity ofwater in the reservoir 5110 may be determined by a measurement of aninertial mass of the water in the reservoir 5110. In one example, theinertial mass of the water in the reservoir 5110 may be determined byimparting a force to the water in the reservoir 5110 and measuring aresponse such as a resulting acceleration of the water or the reservoir5110. The force may be imparted to the body of water in the reservoir5110 in a number of ways, and a resulting acceleration of the water maybe measured to determine to the inertial mass of the water.

In one example (see FIG. 12a ), a reservoir 5110 may comprise a movablepaddle 5112 that extends along a vertical direction of the reservoir5110, and at least partially exposed to the flow of air. In one form,the paddle 5112 may be rotatably fixed to the reservoir 5110 about apaddle axis 5114 (e.g., vertical axis) within the reservoir 5110. Theflow of air in the reservoir 5110 may act on exposed surface areas ofthe paddle 5112 to motivate the paddle 5112 to turn. Conversely, thequantity of water in the reservoir 5110 may resist a movement of thepaddles 5112.

Furthermore, as the quantity of water in the reservoir 5110 changes, thearea of the paddle 5112 exposed to the flow of air may change. This mayhave the effect of changing the force imparted into the paddle 5112 bythe flow of air. At the same time, as the quantity of water changes, theresistance of the body of water to the paddles 5112 turning within thereservoir 5110 may also vary. Therefore, a measurement of movement ofthe paddle 5112 may be a suitable indicative characteristic from whichthe quantity of water may be inferred (e.g., correlated).

In another arrangement of the present technology, a sensor may beconfigured to determine measure of torque produced by the humidifierreservoir 5110. The flow of air may impart force and/or a torque to thereservoir 5110 as it travels therethrough. In some cases, the forceand/or the torque imparted may be dependent on the quantity of waterpresent in the reservoir 5110, as the internal volume of the reservoir5110 that is exposed to the flow of air changes. For example, as thewater quantity in the reservoir 5110 is reduced, the total surface areaexposed to the flow of air may increase. Thus the measurement of torquemay depend on the quantity of water in the humidifier reservoir 5110,and may be also a suitable indicative characteristic. The force and/orthe torque may be measured by any number of sensors such as a load cell,force gauge, strain gauge or others known to those skilled in the art.

5.5.3.4.6 Movable Water Level Indicator

In one arrangement, the humidifier reservoir 5110 may comprise a movableportion configured to move as the quantity of water in the reservoir5110 changes, for example by following the height of the quantity ofwater in the reservoir 5110. In one form, the movable portion may be afloat located on the inside of the reservoir 5110, or it may be a partof the exterior of the reservoir 5110 such as a concertina section thatis configured to move as the water level in the reservoir 5110 changes.The humidifier 5000 may comprise a sensor configured to determine theposition or the height of the movable portion. The sensor may be, amongothers, an optical sensor configured to determine a position of themovable portion as shown in FIG. 11A, an angular sensor configured asshown in FIG. 11B to determine an angular position a pivotably coupledcomponent configured to move with the movable portion, or a proximitysensor configured as shown in FIG. 11C to determine a distance betweenit and the humidifier movable portion.

According to the exemplary arrangement shown in FIG. 11A, the movableportion 5233 is coupled to the reservoir 5110 and configured to moveaccording to a change in height of the water level (e.g., to bepositioned at or near a top surface of the water). In FIG. 11A, wherethe top surface of the water is at a water level of WL-2, the movableportion 5233 may be positioned as shown, and for water levels of WL-1 orWL-3, the movable portion 5233 may be re-positioned accordingly. In thisarrangement, the humidifier 5000 may comprise an optical sensor 5235configured to determine the position of the movable portion 5233. Insome forms, the optical sensor 5235 may comprise a field of view whichspans positions of the movable portion 5233 for a maximum and a minimumallowable quantity of water, for example up to a first boundary of view5235-1 and up to a second boundary of view 5235-2. The optical sensor5235 may then produce a signal to indicate the position of the movableportion 5233 and/or the quantity of water in the reservoir 5110.

In another arrangement, shown in FIG. 11B, an angular sensor 5236 may becoupled to the movable portion 5233 using a connecting portion 5238. Asthe movable portion 5233 moves according to the quantity of water in thereservoir 5110, an angle α between the angular sensor 5236 and theconnecting portion 5238 may be varied. The angular sensor 5236 may beconfigured to determine the angle α to produce a signal to indicate theposition of the movable portion 5233 and/or the quantity of water in thereservoir 5110.

According to a yet another arrangement as shown in FIG. 11C, thehumidifier 5000 may comprise a proximity sensor 5237 to determine aposition of the movable portion 5233. In one example, the proximitysensor 5237 may be located toward the bottom of the humidifier 5000 andconfigured to detect proximity of the movable portion 5233. In such aconfiguration, as the movable portion 5233 moves according to thequantity of water in the reservoir 5110, the proximity sensor 5237 mayproduce a signal to indicate the position of the movable portion 5233and/or the quantity of water in the reservoir 5110.

5.5.3.4.7 Electrical Properties

According to another aspect of the present technology, measurements ofelectrical properties of the body of water in the reservoir 5110 may beused to determine the quantity of water (e.g., by correlation). Forexample, capacitance and/or resistance of the volume of water may bemeasured by one or more sensors. The electrical properties of the bodyof water in the reservoir 5110 may vary according to the quantity of thebody of water. For example, the capacitance of the water may increase asthe quantity of the body of water is increased. Accordingly, electricalproperties of the body of water in the reservoir 5110 may also besuitable indicative characteristics to be used to determine the quantityof water in the reservoir 5110.

5.5.3.4.8 Image Processing

A yet another aspect of the present technology may be use of imageprocessing to determine the quantity of water in the reservoir 5110.According to one arrangement, the humidifier 5000 may comprise a cameraconfigured to capture an image of the water in the reservoir 5110. Theimage may be processed by a controller such as the humidifier controller5250, and analysed to identify features that could be used to determinethe quantity of water (such as the water level).

In some cases, the captured image may be digitised, and then enhanced toaccentuate features such as any boundaries such as an open surface ofthe water or boundaries between the water and the reservoir. Then thecontroller may execute image processing algorithms to extract andclassify the features and any patterns so as to enable the quantity ofwater to be determined.

According to one arrangement of the present technology, the humidifierreservoir 5110 may be configured to enhance a distinction between waterand air in the captured image, such as by improving a visual contrastbetween air, water and the reservoir for instance. In one instance, thereservoir may require a clear ‘window’ to allow the water to be clearlyseen therethrough, or visual markers such as high-contrast surfaces ormarked lines to improve identification of features by the imageprocessing algorithm. Yet further, as the humidifier 5000 may often bein operation in a dark environment such as a bedroom during evening, thehumidifier 5000 may comprise a lighting element to provide illuminationto the reservoir 5110, the camera and/or the water.

5.5.3.4.9 Look-Up Tables or Functions

In any of above methods that may be used to determine, estimate, orinfer, water quantity, it should be understood that one or more look-uptables, one or more functions, or a combination of any numbers both maybe used to relate the measured characteristics to the quantity of waterin the reservoir 5110 (e.g., correlation).

Yet further, it should be noted that indicative characteristics, orvariables, that are used in the look-up tables or functions need not bemeasured directly by a sensor. An indicative characteristic may bedetermined or inferred from measurements of one or more otherproperties. For example, a flow rate of a gas may be inferred from othercharacteristics such as motor speed and electrical current, similarly toas disclosed in U.S. Pat. No. 6,237,593, the entire contents of which isincluded herewithin.

5.5.3.4.10 Learning/Calibration Mode

According to another aspect of the present technology, a humidifier 5000may comprise an algorithm for a learning or calibration mode. A learningmode may modify, populate, or determine a look-up table and/or afunction that correlates the one or more indicative characteristics withthe water quantity.

For instance, in a learning mode, the controller may determine a rate atwhich water is consumed during a therapy session, for example until thereservoir 5110 is empty, or until the end of a session. Then, ifappropriate, the controller may update the look-up table and/or thefunction based on the determined water consumption rates andmeasurements of the one or more relevant indicative characteristics. Inone example, once the look-up table or function for a first indicativecharacteristic to be measured has been calibrated/correlated, the valuesfor other indicative characteristics may be measured/determined and acorrelation table/function therefore may be updated by the controller,based on the known accuracy of the previous look-up table or functionfor the first indicative characteristic.

Alternatively, the humidifier 5000 may comprise an algorithm for acalibration mode, which may be periodically triggered. In one exemplaryarrangement of a calibration mode, a known, predetermined amount ofwater is entered into the humidifier reservoir 5110 and the controllertests how the look-up table or the function performs in determining thewater quantity based on measurements of the indicative characteristicsagainst the known, predetermined amount of water. One such test may bereferred to as a calibration cycle. In some cases, a calibration modemay comprise multiple such calibration cycles for improved accuracy, insome cases with varying amounts of water. For example, the humidifier5000 may instruct its user, such as the patient 1000 or the caregiver tofill the reservoir 5110 to a particular, known amount of water, toundertake calibration. Therefore use of such a calibration mode mayimprove accuracy of the look-up table and/or the function, and may alsocompensate for any inaccuracies that may develop in the system over itslifetime.

A calibration mode may be configured to run at a predetermined interval,such as every six months, and/or at a predetermined time or event, suchas after a treatment period, during an initial set-up process of thehumidifier 5000, during or after manufacturing or prior to sale of thehumidifier 5000. In some instances, the calibration cycle may beperformed by another party than the patient 1000, such as by aclinician, a caregiver or a home medical equipment provider.Alternatively, as described, it may be run during therapy in what may bea learn mode, or it may be arranged to prompt the user at apredetermined interval such as every month.

5.5.3.5 Humidity Delivery Algorithms

Another aspect of the present technology may relate to management ofdelivery of humidity to the flow of air, such as according to thequantity of water present in the humidifier reservoir 5110. Forinstance, a controller may ascertain an average length of a therapysession for the patient 1000 based on a predetermined typical length, orbased on usage data of the patient 1000. Based on the determined averagelength of the therapy session, and the quantity of water determined tobe present in the reservoir 5110, the controller may then determine ahumidity profile to be delivered with the flow of air for the durationof the therapy session. In one example, the controller may determine amaximum output humidity that the patient 1000 may be able to set, so asto be able to deliver a humidified flow of air to the patient 1000throughout a therapy session without running out of water.

According to another aspect, a rate of water usage may be determinedbased on one or more measurements of the quantity of water. For example,rates of water usage may be determined at various times throughout atherapy session by a controller. In some forms, the controller maydetermine a historical profile of water usage throughout the therapysession based on a plurality of measured rates of water usage. In oneform, the controller may adjust one or more humidification settingsbased on the determined historical water usage profile. For example, ifthe water usage rate is above a threshold value (such as, for example,where the threshold value indicates a sustainable rate of consumption ormaximum rate of consumption in reference to remaining time for anaverage or typical therapy session and a determined water quantity), thecontroller may reduce humidification output or a maximum humidifieroutput, and conversely the controller may increase humidification or amaximum humidifier output if the water usage rate is below a thresholdvalue.

As illustrative examples, PCT patent application publication numberWO/2006/015416 discloses, among others, methods of providing profilingdelivery of humidified gas to a patient, potentially to improvebreathing comfort or to maximise efficient use of water. US patentapplication publication number WO/2006/015416 discloses, among others,methods of providing humidity to a flow of air using a humidifier,controlling the absolute or relative humidity of the air to be providedto the patient. Materials disclosed in either application, by themselvesor in combination with each other, may be suitable for use incombination with the present disclosure. The entire contents of bothpatent applications WO/2006/015416 and WO/2006/015416 are incorporatedherein by reference.

5.6 Glossary

For the purposes of the present technology disclosure, in certain formsof the present technology, one or more of the following definitions mayapply. In other forms of the present technology, alternative definitionsmay apply.

5.6.1 General

Air: In certain forms of the present technology, air may be taken tomean atmospheric air, and in other forms of the present technology airmay be taken to mean some other combination of breathable gases, e.g.,atmospheric air enriched with oxygen.

Ambient: In certain forms of the present technology, the term ambientwill be taken to mean (i) external of the treatment system or patient,and (ii) immediately surrounding the treatment system or patient.

For example, ambient humidity with respect to a humidifier may be thehumidity of air immediately surrounding the humidifier, e.g., thehumidity in the room where a patient is sleeping. Such ambient humiditymay be different to the humidity outside the room where a patient issleeping.

In another example, ambient pressure may be the pressure immediatelysurrounding or external to the body.

In certain forms, ambient (e.g., acoustic) noise may be considered to bethe background noise level in the room where a patient is located, otherthan for example, noise generated by a RPT device or emanating from amask or patient interface. Ambient noise may be generated by sourcesoutside the room.

Continuous Positive Airway Pressure (CPAP) therapy: CPAP therapy will betaken to mean the application of a supply of air to an entrance to theairways at a pressure that is continuously positive with respect toatmosphere. The pressure may be approximately constant through arespiratory cycle of a patient. In some forms, the pressure at theentrance to the airways will be slightly higher during exhalation, andslightly lower during inhalation. In some forms, the pressure will varybetween different respiratory cycles of the patient, for example, beingincreased in response to detection of indications of partial upperairway obstruction, and decreased in the absence of indications ofpartial upper airway obstruction.

Patient: A person, whether or not they are suffering from a respiratorydisease.

5.7 Other Remarks

A portion of the disclosure of this patent document contains materialwhich is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in Patent Office patent files orrecords, but otherwise reserves all copyright rights whatsoever.

Unless the context clearly dictates otherwise and where a range ofvalues is provided, it is understood that each intervening value, to thetenth of the unit of the lower limit, between the upper and lower limitof that range, and any other stated or intervening value in that statedrange is encompassed within the technology. The upper and lower limitsof these intervening ranges, which may be independently included in theintervening ranges, are also encompassed within the technology, subjectto any specifically excluded limit in the stated range. Where the statedrange includes one or both of the limits, ranges excluding either orboth of those included limits are also included in the technology.

Furthermore, where a value or values are stated herein as beingimplemented as part of the technology, it is understood that such valuesmay be approximated, unless otherwise stated, and such values may beutilized to any suitable significant digit to the extent that apractical technical implementation may permit or require it.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this technology belongs. Although any methods andmaterials similar or equivalent to those described herein can also beused in the practice or testing of the present technology, a limitednumber of the exemplary methods and materials are described herein.

When a particular material is identified as being used to construct acomponent, obvious alternative materials with similar properties may beused as a substitute. Furthermore, unless specified to the contrary, anyand all components herein described are understood to be capable ofbeing manufactured and, as such, may be manufactured together orseparately.

It must be noted that as used herein and in the appended claims, thesingular forms “a”, “an”, and “the” include their plural equivalents,unless the context clearly dictates otherwise.

All publications mentioned herein are incorporated herein by referencein their entirety to disclose and describe the methods and/or materialswhich are the subject of those publications. The publications discussedherein are provided solely for their disclosure prior to the filing dateof the present application. Nothing herein is to be construed as anadmission that the present technology is not entitled to antedate suchpublication by virtue of prior invention. Further, the dates ofpublication provided may be different from the actual publication dates,which may need to be independently confirmed.

The terms “comprises” and “comprising” should be interpreted asreferring to elements, components, or steps in a non-exclusive manner,indicating that the referenced elements, components, or steps may bepresent, or utilized, or combined with other elements, components, orsteps that are not expressly referenced.

The subject headings used in the detailed description are included onlyfor the ease of reference of the reader and should not be used to limitthe subject matter found throughout the disclosure or the claims. Thesubject headings should not be used in construing the scope of theclaims or the claim limitations.

Although the technology herein has been described with reference toparticular examples, it is to be understood that these examples aremerely illustrative of the principles and applications of thetechnology. In some instances, the terminology and symbols may implyspecific details that are not required to practice the technology. Forexample, although the terms “first” and “second” may be used, unlessotherwise specified, they are not intended to indicate any order but maybe utilised to distinguish between distinct elements. Furthermore,although process steps in the methodologies may be described orillustrated in an order, such an ordering is not required. Those skilledin the art will recognize that such ordering may be modified and/oraspects thereof may be conducted concurrently or even synchronously.

It is therefore to be understood that numerous modifications may be madeto the illustrative examples and that other arrangements may be devisedwithout departing from the spirit and scope of the technology.

5.8 Reference Signs List

Item Reference patient interface 3000 seal-forming structure 3100 plenumchamber 3200 positioning and stabilising structure 3300 vent 3400decoupling structure 3500 connection port 3600 forehead support 3700 RPTdevice 4000 external housing 4010 upper portion 4012 lower portion 4014panel 4015 chassis 4016 handle 4018 pneumatic block 4020 mechanical andpneumatic components 4100 air filter 4110 inlet air filter 4112 outletair filter 4114 inlet muffler 4122 outlet muffler 4124 pressuregenerator 4140 blower 4142 motor 4144 anti-spill back valve 4160 aircircuit 4170 supplemental oxygen 4180 electrical components 4200 PCBA4202 power supply 4210 input device 4220 central controller 4230 clock4232 therapy device controller 4240 protection circuit 4250 memory 4260sensor 4270 pressure sensor 4272 flow rate sensor 4274 motor speedsensor 4276 data communication interface 4280 remote externalcommunication network 4282 local external communication network 4284remote external device 4286 local external device 4288 output device4290 display driver 4292 display 4294 humidifier 5000 humidifier inlet5002 humidifier outlet 5004 humidifier base 5006 humidifier reservoir5110 paddle 5112 paddle axis 5114 reservoir inlet 5118 heating plate5120 reservoir outlet 5122 reservoir dock 5130 locking lever 5135 waterlevel reference 5150 conductive portion 5152 humidifier sensor 5202pressure sensor 5205 flow rate sensor 5210 humidity sensor 5218temperature sensor 5220 vibration source 5232 movable portion 5233vibration sensor 5234 optical sensor 5235 angular sensor 5236 proximitysensor 5237 connecting portion 5238 heating element 5240 humidifiercontroller 5250 central humidifier controller 5251 heating elementcontroller 5252 air circuit controller 5254

1. An apparatus for humidifying a flow of air to be delivered to apatient, the apparatus comprising: an inlet to receive the flow of air;an outlet to emit a humidified flow of air; a humidifier reservoirconfigured to contain a body of water for humidifying the flow of air,the humidifier reservoir being in fluid communication with the inlet andoutlet; a heating element proximate to the humidifier reservoir to heatthe body of water of the humidifier reservoir; a movable portion, themovable portion associated with the humidifier reservoir and configuredto move in relation to the body of water; a sensor configured togenerate a signal indicative of a plurality of positions of the movableportion; and a controller configured to operate the heating element, thecontroller further configured to provide a reference regarding areservoir water quantity of the humidifier reservoir based on thesignal.
 2. The apparatus of claim 1 wherein the sensor comprises any ofan optical sensor, an angular sensor and a proximity sensor.
 3. Theapparatus of any one of claim 1 wherein the movable portion isconfigured to be located inside the humidifier reservoir.
 4. Theapparatus of any one of claim 1 wherein the humidifier reservoircomprises a section external to the humidifier reservoir configured tomove in relation to a change in a water level in the humidifierreservoir, and wherein the movable portion comprises the sectionexternal to the humidifier reservoir.
 5. The apparatus of any one ofclaim 1 wherein the controller is configured with one or more functionsto determine the reservoir water quantity with one or more values fromthe signal.
 6. The apparatus of claim 5 wherein the controller isconfigured to update a function of the one or more functions based onthe determined reservoir water quantity.
 7. The apparatus of any one ofclaim 1 wherein the controller is configured with one or more look-uptables to determine the reservoir water quantity with one or more valuesfrom the signal.
 8. The apparatus of claim 7 wherein the controller isconfigured to update a look-up table of the one or more look-up tablesbased on the determined reservoir water quantity.
 9. The apparatus ofany one of claim 1 wherein the controller is configured to operate acalibration mode to sense a predetermined amount of water entered intothe humidifier reservoir.
 10. The apparatus of any one of claim 1wherein the controller is configured to determine a rate of water usagebased on the signal.
 11. The apparatus of claim 10 wherein thecontroller is configured to control an increase or decrease inhumidification output based on the determined rate of water usage. 12.The apparatus of any one of claim 1 wherein the controller is configuredto determine a humidity profile to be delivered with the flow of air fora duration of a therapy session based on the reservoir water quantity.13. The apparatus of claim 12 wherein the humidity profile comprises amaximum output humidity setting for the duration of the therapy sessionthat permits humidification of the flow of air without running out ofwater.
 14. The apparatus of any one of claim 1 wherein the sensorcomprises an optical sensor configured to determine different positionsof the movable portion.
 15. The apparatus of claim 14 wherein the sensorcomprises a field of view which spans positions of the movable portionfor a maximum and a minimum allowable quantity of water.
 16. Theapparatus of any one of claim 1 wherein the sensor comprises an angularsensor configured to determine an angular position of a pivotablycoupled component configured to move with the movable portion.
 17. Theapparatus of any one of claim 1 wherein the sensor comprises proximitysensor in a vertical location with relative to the movable portion andconfigured to detect a distance between the proximity sensor and themovable portion.
 18. The apparatus of any one of claim 1 wherein themovable portion comprises a float.
 19. The apparatus of any one of claim1 wherein the movable portion is configured to float at a surface of thebody of water.
 20. The apparatus of any one of claim 1 wherein thecontroller is configured to determine the reservoir water quantity of aplurality of different water levels based on the signal.
 21. Theapparatus of any one of claim 1 wherein the reference comprises apercentage of a total volume of the humidifier reservoir.
 22. Theapparatus of any one of claim 1 wherein the controller is configured togenerate an alert or message concerning a reservoir water levelcondition based on a determined reservoir water quantity.
 23. Theapparatus of claim 22 further comprising a communications device,wherein the controller is configured to transmit the generated messagewith the communications device.
 24. A system for humidifying a flow ofair to be delivered to a patient, the system comprising: an inlet meansfor receiving the flow of air; an outlet means for emitting a humidifiedflow of air; a reservoir means for containing a body of water forhumidifying the flow of air, the reservoir means being in fluidcommunication with the inlet and outlet; a heating means proximate tothe reservoir means for heating the body of water of the reservoirmeans; a movable means, associated with the reservoir means, for movingin relation to the body of water; sensing means for generating a signalindicative of a plurality of positions of the movable means; and controlmeans for operating the heating means, the control means further forproviding a reference regarding a reservoir water quantity of thereservoir means based on the signal.